Ribbon cable inside amplifiers

Nothing at all wrong with ribbon cables, if used appropriately. Yes, they are less expensive to assemble with but they do not signal substandard construction.

There are some who are point to point purists and even avoid circuit boards. A practical impossibility except in the simplest of amps.

Not sure about Pass but the ribbons are likely connections to logic boards relating to signal routing relay and remote controls etc., and not signal paths.

Ok thanks, how about the heat in those Class A Pass amps doesn’t affect the ribbon over the long haul?

Op, if poorly placed or not appropriately selected, but true for all components.  Heat is bad so engineers take cooling and material selection 8nto account.

I should add, Nelson Pass has been building large Class-A amplifiers for a very long time and I've never heard anyone complain about their reliability. 

If you feel the need to start poking inside of an amp and making judgements about the parts maybe what you are feeling is a need to build one yourself?  Look up FirstWatt kits.