This episode we learned that Starfleet has transporters which can reach across multiple lightyears.
Possibly, but not certainly.
I thought he meant sensor range and not transporter range. You have to be pretty close for transporters.
But A) we don’t know how close they were and B) we don’t know the effective range of the transporter of DSC.
What we do know is they were close enough to do it and remain undetected. And that’s all we need to know for the story to work.