Correct....many airplane mfr's issued, "thou shall NOT do aerobatics in our planes" many years ago.....regardless of what the original cert or operating manual stated.
That whole, "poop happens, sue everybody" many Americans think they can sue peeps, so mfr's across the board sorta did the same thing, over ride whatever was issued decades ago and the aircraft are capable if maintained and done right...
If....

Granted, most SGS are decades old, most sit outside, no clue on maintenance.
The bulletins were issued more as a hurdle "in case of an incident" by the mfr's.....in my opinion....in case of a lawsuit.