I think the title is misinterpreting what Rybar said. “Deployed” in this case almost certainly means on the other side of the river, but close enough that the bridgehead still falls within its protection. An S300 system is a network of several vehicles, it would be tremendously vulnerable in a small space like a bridgehead. Plus, you’d probably need a pontoon bridge ready to get the system across, and I believe the consensus atm is that the pontoon is still being put together.
Aaah, you're completely right, I get it now that I read it again. Sorry for the misleading title, I genuinely thought they brought it across the river which is completely unnecessary regarding the range of S-300...