Moeck make some moderately expensive recorders with German fingering, and their fingering charts show a fully chromatic two-and-a-bit octaves for the instruments. I am not by any means an expert in these matters, but I did a recorder making course a few years ago and the tutor said that there was a surprising amount of leaway about where you could place the holes – the combination of hole placement, hole size, and the shape of the bore, give lots of possibilities for making slightly different tuning compromises, so it seems to me that there is no particular reason why a German system instrument should be inherantly less in tune with itself than any other recorder. Historically, there were a fair number of fingering systems, and even today there are variations between recorders with German fingering, English/Baroque fingering, renaissance fingering, ganassi fingering, etc. I think the biggest issue wrt progress might be availability of instruments – there is a huge choice of recorders that have English/Baroque fingering, and a very much smaller selection if you want anything else. I have just one recorder with German fingering and it’s absolutely fine to play.