There is no reason to inform users
But you right there is a reason to inform some one is beyond user
But in the other hand some one is beyond user, will figure it out
As for the "bootloop" in dirty flash, it happens when you dirty flash from other ROM. EU ROM is based on china weekly beta but it's a custom ROM and even dirty flash from official china weekly beta can cause crushes and restarts and even bootloop. This is the reason and not the TWRP. Dirty flash is good only when you updating to the same ROM. When you change a ROM even from china to global, it's not good.
May be it's not your first rodeo
But you saying that clean flash is not helping. Or i have misunderstood you
So fastboot ROM is not the same as recovery ROM. The fastboot will flash everything and basically restore your device to the state you have bought it
That's why i took on my self a courage to advice you
If you already have solved your problem, forget it.
Sorry but IT is not physic
But your method of "differential diagnosis" is working in many places
And in IT it sounds like: if something that worked before is not working now, look what has changed
The only thing it doesn't mater what had changed, even if you reinstalled all same software, one of the changes is that you have reinstalled it