I'm willing to bet Honda didn't fix the issue
'87 is the 1st model year TW, after that year the ignition stuff changed. Yamaha probably wouldn't have fixed the issue (if it was even known at the time). My guess is the '87 CDI's problems didn't show face until late enough in the years that Yamaha didn't feel it was financially/marketably beneficial to fix them...it probably just became a 'legacy' part and their focus shifted/remained on current parts.
I'm sure your question is arising from whether your new $250 part is going to go bad in 6 months. I can't answer that, but I'd say you're safe.
ahhh..now that just sucks, at least my original can limp on the shoulder to nearest bus stop, lol
i still dig my oldie t-dub, no need to upgrade