nostr:npub199d7lh2hxsnrd6qa8eyw9ptq6xj5snfgmvpttuy656javaqgrk4qrgxwjc nostr:npub1vg57mtwqr75dmqeaqxmy2nf4nyelcsdp7tlm8tqptjsgpk6c3u4sd28uma

The ? is an end-of-token maker.

Since no additional tokens are required in the first example, the ? is not needed to terminate the link.

It is needed in the second because the time stamp token follows.