If you choose an unknown technology because you have solid reasons to believe it will bring a substantial advantage to the product, which will offset the loss in productivity, then sure. If you choose it just so that your team will be motivated and you willingly take the productivity hit for that, I find it difficult to understand.
It's not the technology choice, it's the reasons that seem weird to me. It's probably because of the runway length they have that they can venture into unknown territory for no reason other than trying things.
I'm reminded of Asana and Lunascript - a fun experiment you can afford when you have lots of money in the bank, but not something I'd see as practical.