Why are we no longer allowed to make a rated seek in a custom position?

I don't understand why they took out the ability to challenge an opponent to a rated game in a custom FEN. I like to challenge players to an opening I like to play which is not included in the book openings list that you can choose from so I challenge them to the FEN of the position. Now, I cannot do it rated anymore. Why?

Also, what if I want to challenge my opponent to a line in an opening that is deeper than just a few ones which are the book opening options offered?

Probably because a lot of custom positions are won from one side and it could be used to boost ratings.

Someone had set up a link a while ago where as soon as you clicked on it you started a custom game against him and were in a lost position. He did in unrated but only to not get in trouble. But he could've easily boosted his rating.

I understand this but at least if they are going to do that they have to add more openings to the book openings option because now if I want to play a less common opening, or an opening but more deeper into it, I can't play it rated

These types of things would just make ratings inaccurate.

including playing games in opening positions not included in the "book openings" option of the site?