I'm not here to talk on behalf of the team, but just to let you know that PDF should be an acceptable format for printing (Tee shirts of otherwise). After all, any printer around will ask you for a PDF as a working file and if you ask for a digital proof, you will be sent back a PDF. It's the issue with print on demand companies only accepting PNGs with transparencies which is a bit problematic.
Obviously it doesn't solve your issue, but in the world of printing companies. PDF is king, and I can understand why the team decided to make it the right format for that.
The straightforward solution would be to be able to change the resolution, which you can do in -say - photoshop (resolution doesn't change the quality, it only indicates to the printing machine which size will the item will be printed in, but there is no way you can by-pass that for the moment unless you change it in a program that allows it.
You can still post in the official feedback (just click on the beaker icon on the top right of the interface)