Bitcoin Core went to the trouble of drafting and publishing a statement over a year ago regarding relay policies:

Bitcoin Core

Bitcoin Core development and transaction relay policy

Bitcoin Core development and transaction relay policy

In order to answer the second question you'd have to figure out how many transactions are showing up in blocks that were never broadcast across the network, which can be pretty tricky to do.

Thank you

Core made the wrong choice and was too stubborn (or too compromised) to admit the mistake and roll it back. They decided that because Libre Relay and Slipstream allowed spammers to bypass node filtering policy, that they would loosen policy by default so the average node was a better reflection of what would actually get mined. They also hoped that Citrea would put all their data in pruneable OP_RETURN instead of obfuscating and embedding it like spammers do. Instead, they should have pushed for tighter consensus rules that would make Libre Relay and Slipstream irrelevant because those spam transactions would be invalid. This is the path BIP-110 is taking us down. Also, Citrea did not change their implementation and continued with their approach to embedding their data like spammers, so Core was wrong about that too.