I see. But then bottom bracket gets higher of course. The rigid fork compensates for that (a bit). It comes at the cost of no front suspension and not being able to quickly fold the handlepost. But this way you can fit an ahead and get a more stable front also more energy efficient when 'stand-n-hammer'. I would also expect this to be ~1kg lighter. Suitcase fold taking the fork out should still be possible. I am wondering why no more Birdys are modified this way as it is so straight forward.

Edit: I have another question here: Did anybody convert a Birdy to singlespeed or even fixed gear? Is it possible without chain tensioner? I now, the fold affects chain length but there are also single speed mods of for example Bomptons (the one from littlepixl is actually fixed gear with a tensioner), Bike Fridays NWT/PRP and Dahon Jetstreams.