I’ve just noticed, while working on my z6 WIP, that Windows Frotz does not seem to pay any attention to the resolution chunk in Blorb files. Peering into the source code a bit, it seems that it does some scaling for Infocom’s z6 games, but otherwise just displays all pictures at a 1:1 scale.
You’ve got a z6 WIP?
I’m very, very curious, please allow me to ask - why? Few interpreters will play it, mobility is out the window, and Glulx does everything you’d need from z6.
Glulx does not, in fact, do everything I’d need from z6. The screen models for Glk (which is what Glulx uses) and z6 are very different, and I’ve always liked the z6 version.
Colour me surprised. I’m curious to see your finished game, to see how it does something Glulx couldn’t.
Can’t say fairer than that. 
Pity few interpreters support it, or support it properly.
As I recall, at the time there were no examples that used that chunk, so I left it alone as not important. If you email me a Blorb file with that in I’ll look into adding it.