The "Zoom to fit when acquisition stops" feature works fine with devices, but not for .sr file apparently. This can be reproduced e.g. with a long file such as dcf77_480s.sr.
It just worked for me for the dcf77_480s.sr file that you mention, as well as for other files (VCD from bug 360). Does the issue still reproduce, or could it have been fixed in the meantime?
*bump*
I can't reproduce the issue. Do keep in mind, btw, that changing the view in any way while the file is loading means that the zoom-to-fit will *not* be performed after the file loaded. The rationale for this behavior is that we don't want to mess up the user's view if he/she wanted to start examining the file before it loaded fully.
Can't reproduce anymore either, closing the bug. Either this was fixed in the mean time or I accidentally clicked / dragged the trace in my tests without noticing or something like that. I fully agree with the rationale you mentioned, that works exactly like it should indeed.