I'm curious...what do you consider 'accordion reeds?'

The Bastari system? Well, obviously. They're on reed
blocks.

But what about what the US maker Button Box (Morse)
does, using 'accordion' reeds that are mounted flat
on the soundboard rather than dovetailed in?

The sound is essentially the same, but there is some
cost and complexity saving, as well as weight saving.
And one could argue that the arrangement is more stable,
as the cause of many a reed 'buzz' is the expansion of
the reedpan impinging on the reed frame, which then
interferes with the reed.

Is this 'legit?'

Or is it a case of 'Morse concertinas aren't as good as
they sound and play?'