TL;DR: The clock oscillator for the sound chip (separate from the main CPU clock, which does not have this issue) appears to be speeding up over time as it ages. Games from that era use video signal synchronization to regulate their overall speed, so this will not affect game times. It may cause audio glitches or crashes, but it won’t make games run faster. However, it has the potential to cause (and probably has caused) desynchronization issues with tool-assisted speedruns on original hardware.

(I looked into this a bit for another post of this same article.)