Don't core devs test out new versions for a few months before releasing it to the public?
nostr:npub1a2cww4kn9wqte4ry70vyfwqyqvpswksna27rtxd8vty6c74era8sdcw83a asked a great question yesterday: why no temporary softforks?
Here's Base58's niftynei on the difficulty with adding opcodes to bitcoin
Discussion
New versions are tested on Testnet, signets, or locally with regtest Bitcoin. But until it's live on mainnet it's effectively just like testing it on a completely separate fork