That is not what I am saying. Personal dumps and proper scene releases are no different to each other. They both lack the extra black box magic which current tools cannot extract. Neither .XCI files nor retail cartridges changed after firmware 9.2 was introduced. Therefore its logical to surmise that Nintendo introduced a check that backups cannot pass because Nintendo is aware of what we lack.
Since the lotus firmware is still a Blackbox, in theory it could even be already existing and dumpeable data, that is used to generate the right result in the gamecard asic, from the seed comming from nintendos server.
But to know what exactly is done and allow online again, the lotus firmware would need to be reversed either way, otherwise everything from the seed entering the gamecard asic to retrieving the return value is just speculation anyway ^^
About nsps, as far as I know they where detectable all along, since the tickets contain a cert similar to the one used in gamecards, that was always used for authentication when going online.
And as far as I know the seed authentication part added in 9.x is only used for game cards since only they have a dedicated asic that can run code for generating the result, at least that's what I took away from the discussion of multiple of the devs in the switch scene.
About tx having not added a fix for it yet, either they didn't find a way to access the decrypted gamecard asic firmware, or what I thin is more likely, they didn't try to fix it, since it only affects a small percentage of their userbase, and going online in sxos was never officially support anyway.