It's true that Google gets to see them, but Apple is no better in that regard: they store your collections on their servers too (where else would they store them?).
End-to-end encryption
Maps keeps your personal data in sync across all your devices using end-to-end encryption. Your Significant Locations and collections are encrypted end-to-end so Apple cannot read them. And when you share your ETA with other Maps users, Apple can’t see your location.
Other useful sections on that page worth reading: "Location Fuzzing", "Random Identifiers", and "(on-device) Personalization"
Don't spread misinformation on privacy, it'll mislead people into sharing too much data.
I would have assumed that shared collections with a group of iCloud accounts would be e2e encrypted like iMessage groups are e2e encrypted. Glad to revisit that assumption.