I have a Birdy with ETRTO 349 wheels and 40mm wide tires (Greenspeed Scorcher, 43mm in practice at 7bar). These tires are very fast and nevertheless, my current transmission = 52-16 front and 9-32 rear provides long enough developments (something around 9.3m).

58-9 seems to me not necessary with my tires that have an overall diameter of 435mm and surely not with ETRTO 406 wheel and 28x406 tires (overall diameter of 462mm.

Note that I tried to put ETRTO 406 wheels with Schwalbe Pro-one 28-406 tires that are in practice about 32mm wide on my Birdy and that this wasn't possible with the mudguards (the mudguards self are OK but the fastening of the mudguards hit the tire. It could be possible to make it fit with some modification of the mudguards fastening).

Pacific Cycles indeed sells Bidy without mudguards but also sells mudguards.

It seems to me normal to sell a sport oriented Birdy without mudguards same as for all sport road bikes.

A picture of the folded Birdy R+ with dropbar, seems OK ?