This sounds like it's the same thing as the thermal pad mod for the M1 MacBook Air.
On the upside, you get better sustained performance and it lasts nearly just as long as the Pro, from what I recall. On the downside, it elevated the temperature of the backside aluminum to a high enough temperature to be able to cause burns (something like 80-90C). Not a huge issue if you always use it on a table or something, but if you truly use it as a 'lap' top, it'll be quite unpleasant.
On the upside, you get better sustained performance and it lasts nearly just as long as the Pro, from what I recall. On the downside, it elevated the temperature of the backside aluminum to a high enough temperature to be able to cause burns (something like 80-90C). Not a huge issue if you always use it on a table or something, but if you truly use it as a 'lap' top, it'll be quite unpleasant.