I haven't maxed out a single tree yet; but I do split my points between 2 trees usually.  I think it might be difficult to max out 1 tree, let alone max out a 2nd tree, and probably borderline impossible to max out all 3 trees in one game. Also, I'm not even certain the AI will select options from an ideology tree that is not it's primary designated ideology. But your first sentence said all that really needed to be said...

"I have not played the game yet"

Don't worry about theorycrafting until you have played

aerez4546: "I'm not even certain the AI will select options from an ideology tree that is not it's primary designated ideology."

Answer: Only that would be fair! Every other thing could give the AI a significant advantage.

@MottiKhan No I don't have a choice if I am truly committed to my loved ideology That is exactly my problem here.

In a very long game on a big map the AI might only win just because of going for the next tree :-/  Unspent points are not nice to have. No matter if it is 1 or 7 points.

If aerez4546 is right it does not matter. But if he is wrong it matters!

Would be great to hear an official statement.

Moderator? Programmer?  Can you please comment on this one? Thank you!

I am not sure that the devs will address this at this time but your best chance would be to edit your OP to move it to the support forum. The devs do not monitor the entire board.