I was a bit loose with my language- I know the designer were far from stupid! I still don’t see why they didn’t go battery clip in the mk1 though- a soldered battery implies you want the user to return it to manufacturer or some other tech service. By the time it runs out they no longer support the mk1 
One interesting implementation I’ve come across is the k2000 from Kurzweil- the batteries are literally AAs in a normal battery compartment. Those might have their downsides for this kind of application (in addition to size) but they’re very nice when you need to replace them!