But he has.

Then you come to even more complex options as well. The most interesting thing to me personally is that with other products you have ways to extend them by plugging things in, where as with Jolla devices you may snap on a cover that adds other functionality. For example, if you’re going to a club you might want to snap on a back that has a big flash and maybe a big camera button or something. You might also want additional battery capacity, and you may also use a cover with at thin battery to bring that functionality. The sky is the limit and we’re open for collaboration and ideas here, and these interfaces and features will be open to third parties to allow them to create other apps and features for Jolla.

Call it speculation, but to me it seems that kind of functionality is next to impossible to do without any physical connectors to phone.