It don't matter since the code is open source & pretty damn solid both server side & client side
There again is something we need to trust on Threema's side .. You know even nostr:nprofile1qqsgydql3q4ka27d9wnlrmus4tvkrnc8ftc4h8h5fgyln54gl0a7dgspp4mhxue69uhkummn9ekx7mqpzemhxue69uhhyetvv9ujuurjd9kkzmpwdejhgqg4waehxw309aex2mrp0yhx6mmnw3ezuur4vgkhjsen put a pretty sum to help nostr:nprofile1qqsvnx99ww0sfall7gpv2jtz4ftc9v6wevgdd7g4hh7awkpfvwlezugpz4mhxue69uhkummnw3ezummcw3ezuer9wchsx06t26
Also with the IP tracking pretty hard now they have nostr:nprofile1qqsgmff9zpdwhldyelnne99xafacy7a0xxwgydw7vnmsrmvy8h5257sppemhxue69uhkummn9ekx7mp0wxv9gq nodes as well ..
But like with Tor browser or nodes relays if only governments run it they could probably track something so help decentralized the internet 😅