[Lawrie]

I'd guess the Export is intended to be editable in Adobe, whereas the print version is a minimal rendering.
<snip>

Maybe, but I'm more inclined to put it down to everything micro$oft does is like me, significantly overweight 

FWIW I don't use adobe products at all, nor am I any kind of programmer, but other PDF tools seem to handle edits and markups of my printed* PDFs just fine.

* I've used a variety of PDF printer apps over the years and they all seem to have produced perfectly compliant PDF documents so although I didn't test it, I'd be surprised if Adobe was unable to correctly edit these files.  There is no doubt Mobile Sheets handles them perfectly too.