other implementations have code available since last year..
even today core doesnt have live segwit code today.
real segwit code has not been running on bitcoin mainnet.
yet many implementations have been running 2mb block rule on bitcoin mainnet since last year
Having code available isn't any good if no-one on the network you're trying to hijack is willing to let it happen. If alternatives are running 2MB block rules, where are all the 2MB blocks?
Oh that's right, Core is the network, and those competing protocol clients run Core's rules.
That means they can't run their rules on the Bitcoin network, as they've can't make valid blocks to apply the rule to. And they've never been tested on a 10 billion dollar economy, but they have been tested in Franky's basement room testnet, connected up to a handful of others, lol