It could be that if enough miners connect to port 3301 they alter the version number (without using XT) on the block itself that gets relayed, expressing support for the BIP but not using the flawed XT implementation?
And with that, it's obvious that the pool operators should indeed be more specific in what
exactly is on the back-end of the 3301 port. There's at least 3 readily accessible possibilities;
1. Bitcoin-XT, which has the block vote but also already contains the additional other changes.
2. Big-block only, which has the block vote and all code to handle big blocks, but does not contain the additional other changes.
3. Not-XT, which only pretends to be XT and sets the version number (thus voting), but does not actually have the code to handle big blocks (or any of the parts that take votes into account)
While all 3 constitute a 'vote for' big blocks, the devil is in the details. I highly doubt it's the third option as that would basically be double-crossing those who explicitly chose to mine at that port expecting either the first or second option, but that still leaves those two. Can't hurt to clarify the particulars
