They're doing a soft fork. But it's a minority soft fork and they're right now getting less than 1% of blocks per signaling period. If they get 51% of the hashrate they can pull Bitcoin along with their 'upgrade.' Otherwise their chain splits off because they throw away the blocks in the heaviest chain due to the rules of their BIP. Some do seem to not recognize this is how soft forks work believing that only hard forks cause chainsplits. So indeed some will be quite surprised. Others just believe that miners will have an 11th hour capitulation to avoid having blocks thrown out. But as far as I can tell miners couldn't care less about these non-merchant (aka non-economic) nodes.