"There's a misconception when it comes to bet sizing. As it turns out, when playing GTO, all sizes will show almost exactly the same performance. You can check this for yourself, by building the same tree, but for different sizes. After that, check the overall performance for OOP. As you'll find, all EVs will be nearly the same, and any bet size should basically work.

What is really important when it comes to your performance is your quality of play; the bet sizing has almost no influence whatsoever; for any size there's a strategy that performs almost exactly the same as any other size. A consequence of this is that the approach of using multiple sizes (to see which one occurs most) doesn't really work. Within a given dEV there's several different configurations of betting frequencies that all lead to the same result. You're basically looking at static. Bet sizing is really not something to be overly obsessed with; there's almost nothing to be gained here as opposed to focussing on your quality of play."

This has been spinning me for quite some time ..
I don't have much experience with solvers, but trying to improve I try to find ways to simplify strategies.

How true is this?

if it were true, what only bet would OTT and OTR choose in the following sequences? (assuming we can also push all OTR)

At 100bb
Pot 5bb
* SRP IP
* SRP OOP

At 100bb
Pot 24bb
* 3bet OOP

At 100bb
Pot16.5-19bb
* 3bet IP