^Apples to oranges. The floating office is just that, an office. Its purpose was to provide the refit engineering team with a meeting site separate from the Enterprise itself. The spacedock seen in TSFS was intended to house several ships, so of course it would have be much larger than Enterprise or any other vessel inside of it.
I thought of something along those lines, too, that it would have been difficult to stage an exciting escape scene from the office-station. I suppose a good writer could have done it. That would not be me.
I suppose I just go for the right-on-the-edge-of-believability of the office.
spacedock didn't really start to bother me until years after the fact. It just seemed too fanciful for the time. 27th century or something, maybe...but not 23rd.
Pretty fair chance in my mind that they were basically running away from anything TMP