The built in "Phone" feature/thing of the N800 will only work with a DUN device and as your PPC doesn't support DUN (this is why I liked my Os2003 with widcomm hacked bluetooth stack :P), I don't really see the point in making it force to show up (I'm not sure how it would be done anyway except for changing the gconf entries)

But from what I know how maemo-pan works, it finds the device configured as a phone and makes the Bluetooth-Pan connection entry, which it seems to have done, what happens if you try connecting through that? (I get a bubble saying Bluetooth Pan is connecting to my phone which fails because my phones only do DUN :P)