Hard to say why companies do not want folks experimenting? My guess is they made it and know it does just fine as is, So why fool around, And then folks blame the company when fooling around screws it up! Same for all tweaks. The main place I use the higher frequency had been my old bought $250 used DA, and the $40 bought used five disc CD changers. Not much money on the table.
On my own Bryston BP-26 I have not tried the higher Hz AC. but I have tried both 'Technical power'/ balanced power 60V/60V and normal 120V/0V from my Furman conditioner. The balanced power does also make the Bryston a little warmer. and the sound has greater clarity but slightly leaner. vs normal AC.
I have my Marantz Sa-10 connected to the AC via the 'Technical power' 60V/60V from my Furman REF 20i ... this means the HOT line is only 60V but the 'Neutral' line is also 60V (in the same way in US homes 240 is split and is 120V hot and 120V neutral to produce a total of 240V) Some devices have trouble with balanced power. Particularly tube with direct heater (so I have read.. I have no experience, but have run my own tube preamps with balanced power, no problems, just the same slightly leaner cleaner sound with 60V/60V.)
On my own Bryston BP-26 I have not tried the higher Hz AC. but I have tried both 'Technical power'/ balanced power 60V/60V and normal 120V/0V from my Furman conditioner. The balanced power does also make the Bryston a little warmer. and the sound has greater clarity but slightly leaner. vs normal AC.
I have my Marantz Sa-10 connected to the AC via the 'Technical power' 60V/60V from my Furman REF 20i ... this means the HOT line is only 60V but the 'Neutral' line is also 60V (in the same way in US homes 240 is split and is 120V hot and 120V neutral to produce a total of 240V) Some devices have trouble with balanced power. Particularly tube with direct heater (so I have read.. I have no experience, but have run my own tube preamps with balanced power, no problems, just the same slightly leaner cleaner sound with 60V/60V.)

