I got a 404 error when I tried to get to your link.
If there has been a lot of work done on the power amp board, then there's no way to know what has been done unless you compare it to the original schematic. It may simply be that a number of parts need to be replaced and because the driver transistors were no longer available newer style parts were used which have different casings and look wrong, but they may be perfectly fine as replacements.
Or it could be that someone thought that they could modify the circuit to make it better in some way or another.