Maybe a lawyer could make a different argument, but under how I was taught and trained they at least seized the tires. It materially interfered with the use of the tires as intended, and would therefore be a seizure. Note that if they are liable is a different question, and honestly if it's a seizure or not is really not the most important question in that regard. The case law I'm familiar with on damaging property is almost entirely in the context of serving a search warrant, probably because that's where the question usually comes up. It's always been held to be a reasonableness standard under the 4th amendment even if not considered a seizure (cutting holes in dry wall may not be a "seizure" of the wall, but still must be reasonable).