I took my late '98 v70 with 78k miles for a t-belt change today and my friendly local volvo dealer informed me that my '98 has a year '99 t-belt/mechanical tensioner design and these are replaced at 105k miles.

So the good news is that indeed that Volvo TSB #2210015 is correct:

If you own a late '98 s70/v70 (say built 5/98 or later) with engine serial #1266128- or greater, the engine most likely has a '99 design t-belt that comes with a mechanical tensioner. The good news is, they need replacement at 105k miles, the bad news is that the mechanical tensioner has to be replaced at the same time, and this should be left to the pros, not a diy job.

Hope this helps someone with a late model '98 70 series.

Cheers.
--
'88 240, '92 740, '98 v70 GLT John in Tampa Bay