I've noticed that (on English Wikipedia at least) where <mapframe> is used without latitude and longitude specified in the tag, the automatic zoom and centering only works on page preview.
Example:
* https://en.wikipedia.org/wiki/Template:Maplink/doc#Usage shows a map with geoline data from [[https://www.wikidata.org/wiki/Q1094308|Q1094308]]
** Most of Europe and the top half of Africa is visible in the frame, and the line featured isn't centered in the frame
* https://en.wikipedia.org/w/index.php?title=Template:Maplink/doc&action=edit§ion=2 (push the show preview button if you don't have the 'Show preview on first edit' preference enables)
** The frame is zoomed and centered such that the line feature is centred in the frame, and just fits within its extents
See [[https://en.wikipedia.org/w/index.php?title=User:Evad37/Sandbox_2&oldid=839067740]] for a plain example without the template. The same behaviour occurs.
Viewing the page should give the same result as previewing the page (otherwise what's the point of preview?); preferably both should have auto-zooming and centering.