Possible justification of playing 1. e3 as white

Total garbage and hogwash!  You do not play an opening with the expectation of tricking the opponent.  Wrong way to learn chess.  People are smarter than you think!

1.e3 d5 2.d4, Black can play 2...c5 instead of 2...Nf6 to take advantage of White's slow play.  Also, after your 2...Nf6 3.c4, thank you for not developing your Bishop.  No pressure on the dark squares and no threat to trade off my good Bishop.

Also possible is 1...Nf6, which you do not account for, staying Flexible!

And then for anyone that plays 1.e4, They can play 1...e5! And after you 2.e4, THANK YOU for letting me go first with Black!  Now I have the slight advantage that you SHOULD have for having the White pieces!

The only positive thing I can say about 1.e3 is that it has not been refuted!  Other than that, 1.e3 is hot garbage!

It does break the rule of moving a major piece twice, e-pawn. Other than that it is a fine opening.

1. e3 is fine. There's no need to believe people who don't know that.

In more seriousness than my above post, I definitely wouldn't call 1. e3 "hot garbage." It's just an equal chess opening, like the Nimzo-Larsen or the Orangutan or the KIA or whatever and you won't lose because of it (altho if you're a master you might struggle getting any advantage as white consistently).

Say like 1. e3 d5 2. c4 first of all, that seems reasonable esp for someone like me who has sometimes played 1. Nf3 2. c4 or 1. Nf3 d5 2. e3 and 3. c4. I'd play this, but you could also play 2. d4 and transpose into a Colle, or of course 2. Nf3 would transpose into a position I've played before pretty often.

1. e3 e5 and you have a choice. You can play 2. d4 and now black should probably take it (since 2...e4 3. c4 is nice), after which we transpose into an Exchange French which is equal but some players like to play this opening. Or you can play 2. c4 and that's a type of English, or 2. b3 and that's a type of Larsen.

1...Nf6 is flexible but so was 1. e3, so white can play any of 2. b3, 2. Nf3, 2. d4 or 2. c4 with an equal position and then play positional chess.

I know not much of the book was about 1. e3 per se, but there's a reason "e3 Poison" was a thing. It's not a bad idea. No it's not ambitious but "the position is not equal if the players are not equal." And if you want to take your opp out of prep and just play a chess game based on understanding I actually think you could do a lot worse than 1. e3.

Also food for thought: the game of chess clearly ends in a draw with best play after 1. e4, 1. d4, 1. Nf3, 1. c4 etc and 1. e3 is the same. So that being the case, I've often considered that maybe the entire concept of "advantage" is subjective (because someday in the far-off future there could exist 32 piece tablebases and such) and maybe it's just all a question of putting practical pressure on the opponent and making them find good moves consistently until, after enough errors, it becomes winning. Which is what chess should be all about anyway: outplaying the opponent from a chess position.

Sorry that was d3, not e3

I won; that’s all that matters. And I beat an 1800 player playing one minute bullet game. He’s the one who played terrible, not me.