Yep, the very high efficiency cells are typically reserved for highly specialized areas where cost doesn’t matter.. You’ll see Boeing’s name a lot near the top of the efficiency list for the exotic cell types, their lab’s website should clue everyone in to what their main purpose is: https://www.spectrolab.com

They list 31% efficiencies for their cells that can fly today which must be near the limit of commercialization / certification. Still pretty good though, that’s 50% more efficient than a standard panel, and at several $10s of thousands per kg into space, clearly worth it!