If I were those guys I wouldn’t want someone random person re-encoding in order to shrink it down.
I used Harmy’s x264 settings to get 2.7 just right. And njvc went through some some hassle to include it without re encoding. so just telling BDRB to build it smaller will lead to quality loss, whether it was visible at a glance or not.
The point of the 25gb versions was more discs but same quality. compressing everything, including a film where quality matters, and some YouTube rips where, not so much, may not be the best approach.