@Elroch: We've come closer on nothing but the minimax analysis. Indeed you need not provide all the white options only all the black ones which is let's say just 1483664754 variations. That's quite a bit more than 1. "Forced mate" and "forced win" are total non-concepts that replace proof with a result. It is loosely used to suggest that a proof can be delivered in a few lines - taking into account the knowledge level of a decent chess player". The truth is that unless a win or a mate is a forced mate it is not a win or mate at all. A truth seeker will never use the term "forced anything". It does have a deeper meaning though. It's another way of saying "we are playing fighting chess". Fighting chess is the description of the relationship between the 2 parties in a chess game with regard to a goal and their presumed relationship in solving certain composition types like studies and directmates. It is not universal as it is replaced by different strategies and goals for helpmates and selfmates. The fighting condition is not self-evident in goals and strategies of composition land. What we know as minimax evaluations formalizes the decisions in fighting strategy and thus all "forced" outcomes.
Btw, "winning strategy" is either meaningless in proofs or it is also the same as "forced win" and "fighting win". The way the term "strategy" is used in chess game analyses is 90% based on the knowledge level of players and seeks to avoid delivering actual proof lines. But I suppose you know that.
Indeed, you know nothing about "solving". Though chess compositions have a solution they are not made "to be solved". They are made to present a panoramic view of ideas in the composer's mind. The solving approach is an elegant way to demonstrate them plus a challenge for the mind. Did you know that most readers of composition magazines do not seriously attempt to solve the challenges? They much rather browse through the solutions and comments to enjoy the views. And the last thing any composer will want the solvers to get away with is some accidental solution. His task of course to prevent that. He only wants to see it "solved" in the exact way he created it because that is his piece of art. And that includes for instance "the thematic white failures" which are lost in the pruned minimax analysis. And it includes discarding the lines not showing any part of his artistic creation. They only muddy the scenery. Therefore in solving competitions the focus is on thematic content. Providing 1 thematic solution line gets you a point while 6 others may get you naught. There is some arbitrariness in the judging of solutions and points and referees have backroom discussions about it with solvers (occasionally). Just to show that solving is not about mathematical proof.
Your sort of solving is imaginary. - not only because it is uninteresting but also because it is undoable for any but the simplest puzzles - unless of course you are cheating with non-existent forced win lines and computer or poster generated counterplay. You missed out on the design perspective as much as the math requirements.

Back to chess, I am only interested in truth (i.e. the solving of positions to evaluate results and how to achieve them). Sorry for the offense this may cause. I am agnostic about the preferences of the chess composition field, and whether a position is an endgame study or a problem doesn't have any fundamental relevance to solving it: the objective and the rules of chess are all that matter.
Being interested only in the objective truth of a chess position is fine, and this probably parallels your preference for objective truth in the real world, i.e. the scientific perspective. If you're into philosophy, we can consider how most complex things have both a subjective aspect (e.g. artistic) and an objective one (e.g. physical sciences). Thus a painting has both subjective/artistic properties (in the minds of viewers) and objective/physical properties (its paints and wood). Likewise a chess composition, where its objective "truth" – win in X moves or draw – is uncovered by analysis or tools like tablebases.
The issue of soundness/unique play, though closely related to the artistic, actually belongs to the objective side. This is why, even though it's normal for problemists to have different (subjective) views on the value of a composition, they practically never disagree on whether it's sound. Soundness is on a higher objective level compared with the more fundamental "win/draw" lower level. Using paintings as an analogy, soundness is the colour/chemical properties while win/draw is the particle-physics properties.
It's fine to focus on the objective side of things, as scientists do, but this can be carried too far when subjective things are devalued or viewed as just illusions (e.g. emotions are nothing more than chemical processes in the brain). That's a type of reductionism common in the modern world.