This is a poor system that would probably have been improved by TNG and would probably not be allowed in a civilian job. But in a TOS-era Starfleet job, this risky operator-judgment-intensive procedure was seen as acceptable.
It's really ridiculous any way you cut it. Why would someone need to be INSIDE the pod to take measurements? You are asking for trouble? Given that the whole case hinged on something that was never well explained (what the pod was, why someone had to be inside it, why it had to be jettisoned, why Finney wasn't given enough time to get out, why bridge camera records weren't the very first piece of evidence consulted, etc), it just throws this ep on the pile of 'bad Trek episodes', which is a shame, as it wouldn't have taken much effort to make the central conundrum the same without having such a contorted, hard-to-explain scenario at the core of it.