I would argue relays are centralised, a relay is run by someone that can apply censorship, the power of Nostr is the multi relays approach.

However the way I see it what nostr:nprofile1qqsp0c5gn7aqzqsaqj9p8lgt5yy26vwrsvnzj4rqcg0xn3pl4ra729gpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsz9mhwden5te0wfjkccte9ec8y6tdv9kzumn9wshsz9thwden5te0wfjkccte9eskuem0wghxjme0fls0tc is trying to achieve here is scaling Nostr to regular users who have less of a notion about decentralisation, such users need easy/simple access to Nostr, but they can later take a more decentralised stance.

Regarding legality, just invest as anon your keys are your proof of investment.