The mere existence of someone is not really PII. You don't know that I did that search, nor can you connect to anything else... and this is a constructed example in which I try to jam some sort of PII into a single search is itself a bizarre example that probably corresponds to fewer than 1 in 100,000 or 1 in 1,000,000 searches, if that. When's the last time you stuck your own PII into a search box and connected it to something of some sort of significance? It's a very small edge case.

A search history can reveal many things about a person. The mere fact that someone, somewhere searched for "star wars harry potter crossover slash", unconnected to any other search item, doesn't reveal anything about anybody.