As another reply notes, this is a very strange burden of proof you're suggesting. That said...
I don't think modeling Google as a surveillance company is a particularly good model. If you need to pick something reductionist, it's probably safest to model Google as a corporation that seeks to make money, although that's not particularly unique or (obviously) a sufficiently refined model.
I use a lot of Google services, own some Google hardware (phone, smart speakers and the like). But I also have reservations and concerns about Google, and I try to regularly reexamine my relationship with Google to see if I'm still comfortable with everything!
One step I took was to really dig into the My Activity dashboard that Google provides. I was really interested, after letting a Google Home into my life, to see what I could learn. The most obvious step I took was to listen to the recordings Google keeps of every interaction I have with the Home, and ensure there weren't things presented that I hadn't intended Google to be listening to.
But! What if Google is actually recording everything, and then only presenting me with the things that were actual instructions to my Google Home in the dashboard? (Let's disregard network traffic analysis and the like for the moment.) If Google were up to this kind of shenanigans, they would have to be very, very careful to have an appropriately conservative filter in place to ensure none of the secret recordings were ever presented to me.
So, to test this, I proceeded to independently record every interaction I had with the Google Home (just took a quick note on paper) for a couple days. I later went to the My Activity dashboard to see if every interaction was present. (They were.) At this point, I am reduced to a narrower set of options: Google is actually doing what they told me they would, or their super-AI is so advanced that is is capable of covert monitoring and reporting on my activity along with _perfect_ filtering such that there are no false positives or false negatives.
This obviously isn't exhaustive or comprehensive. But I find myself coming back to "why?" The things that Google tells me they do with my data, up front, are sufficient to explain their business activities and revenues. The disincentives around doing anything more nefarious are rather large. I reevaluate the relationship periodically, but I am generally comfortable looking at the terms of the deal (I share some data, they provide me a lot of value) and accepting them.
Honestly, the thing I find far scarier is their absolute shit-tier support and draconian account suspension policies. I found myself entertaining becoming a Google One subscriber even though I have no need for more cloud storage. I was literally entertaining the notion of paying them a nominal fee every month so that I might be somewhat less likely to lose my account and all of the association information for some minor (possibly merely perceived) transgression. That's a bit scary!