Short version: 8 year old winter tires probably need to be replaced.
Bulges in tread area are bad - but I’m guessing that wasn’t what the garage was pointing out. These are winter tires and heat is the tire killer - AND - the garage probably wouldn’t have shrugged it off.
Bugles in the sidewall are less problematic - and my guess is that it was small and probably due to some small imperfection in the manufacturing process.
The tire industry seems to have settled on removing winter tires when they reach 4mm (5/32nds of an inch). And since short hauls tend to wear tires more rapidly, my guess is that these tires are near that point.
Traction is lost long before the tire appears to be worn out - and since it is pretty much proportional to tread depth (at least for snow traction), these tires are likely borderline.
And 8 year old tires are probably OK for a couple more years agewise. Tires age more slowly in cold climates and in Canada, it’s about 10 years.