Are these holes in my garage's wall indicative of flushing out carpenter ants?

I just bought a home and discovered a substantial amount of wood rot in the garage. I had to tear away a lot of drywall to see it, and when I did, I found obvious evidence of carpenter ants. However, there are no ants left, no corpses, the entire colony seems empty.

Now, our contract with the sellers clearly states that there have been no pests or wood destroying organisms in the time that they’ve owned the home, but I don’t believe that at all. They’ve been there for 33 years and have made modifications to the garage, including adding insulation and drywall (dated 88 and 2001 respectively) and building a second garage that adjoins to the first in 1994. I find it extraordinarily difficult to believe that the rot I’m seeing has been present for over 33 years, it seems to me that it should be far worse by now if that was the case.

This picture shows the rot in the corner of the garage, which is adjoined to the addition garage from 1994. If the owners were being truthful, I’m to believe that they built this addition with pest-induced rot so bad that you could see daylight through the siding? Sounds absurd to me. They even reinforced (poorly) the structural members. That concrete is also only in the corner, the rest of that wall has wood right on top of the dirt.

Clearly there have been repairs done. It’s a question of whether or not there was an infestation during their period of ownership, which brings us to these holes in the drywall (this is the same wall as the previous photo):

You can see another one to the left where I removed the drywall, but it’s the same kind of hole. This to me looks suspiciously like some kind of hole for gassing or otherwise injecting something to kill the ants. (the fan in the middle is some exhaust to outside and I figure is unrelated)

This is an up close shot of the white junk that was injected into the hole.

Obviously I’m consulting professional carpenters and exterminators, but does anyone have any experience with this kind of thing? If this really is obviously a treated infestation then I’m planning on getting some kind of statement from an exterminator and/or carpenter and pursuing legal action. I’m not sure if the sellers lied or just messed up their contract and didn’t understand what they signed, but they’re still on the hook in Washington state if they improperly disclose defects.

Some other shots showing clear evidence of a carpenter ant colony:

Thanks!