Why would they make U-Turn weaker?
Literally only for Scizor. You know, the Pokemon who famously never uses Technician because it doesn't get any moves that synergize with it. It really is baffling why Game Freak would go so long without giving Scizor a Technician tool that it can make its own.
60 power U-turn and Tough Claws Weavile are things Arkm has already complained about it the Unpopular Opinions thread. It seems they have realized other threads exist, but still haven't quite grasped that this subforum isn't a place to pitch their ideas for a community ROM hack. The bit about special and mixed attackers is new, though.
Here are the number of physical, special, and mixed attackers, assuming it requires an offensive stat greater than or equal to 90 to be considered proficient.
Physical: 203
Special: 133
Mixed: 137
Here are the results again, filtered for fully evolved Pokemon.
Physical: 166
Special: 104
Mixed: 125
While there significantly more physical attackers than special or mixed attackers, about 1.5x more than either and making up about 40% of all offensive Pokemon as a whole, I would not go so far as to say there "so few" special and mixed attackers.
Showdown commands used in the methodology:
/nds attack >= 90, special attack < 90
/nds attack < 90, special attack >= 90
/nds attack >= 90, special attack >= 90
/nds attack >= 90, special attack < 90, fe
/nds attack < 90, special attack >= 90, fe
/nds attack >= 90, special attack >= 90, fe