[xiphias]

They didn't adapt. BCH created a new op code for replay protection, so it's trivial to create a transaction to at least cash out BCH. It just doesn't take 5 to change a bit in a transaction before signing. Also they can just copy open source code that does this already well.

[makomk]

That bit is just a flag which indicates that how the actual signatures on the transaction are done has changed. In order to create a valid transaction you have to implement those changes too, and not all the open source code that claims to do this actually gets it right. And of course, being able to build transactions is just part of what you have to do to support a new coin.