This is a non-issue. No one needs permission to start his own signet network with whatever consensus rules they want and do any kind of test on a persistent network that mimicks mainnet even better than testnet.

Additional context: signet is a new kind of testnet introduced in 2020 that is meant to address testnet's shortcomings. Testnet sometimes doesn't see any new blocks for hours, or hundreds of blocks come in at once, leading to huge chain reorganizations. This is no good at all to test real life scenarios.

In comparison signet doesn't use proof of work to validate new blocks. Blocks are simply accepted if they come signed with the private key of the entity who bootstrapped the network. And that entity can "mine" (rather issue) new blocks at whatever rate they want (usually every 10 minutes).

There is an default/official Bitcoin signet which Bitcoin Core connects to when started in signet mode, but this mode is designed to be used by anyone who wants. E.g. the Mutiny Wallet team runs their own signet blockchain.

Ordinal theory doesn't need a BIP because it's doesn't really have anything to do with Bitcoin and it's a scam, not an improvement.

Additional context: Ordinal theory claims to be able to differentiate the different "1's" inside number 4, and assign them an identifier. And further claims that when you do math like 4-1 you're able to tell which number 1 you removed from the number 4. It really is just a scam to separate fools from their sats.

I'd consider the BIP review process compromised if a draft for such nonsense got accepted and assigned a BIP number.