Yes, it would.

If Jolla were to die tomorrow, the UI dies with it. Again. The same as has happened with the N900 and N9, to varying degrees. The same as has happened with various other consumer electronics products over time.

Having the source code available helps stave off untimely obsolescence, and possibly even opens up new and more interesting avenues of putting it on more hardware, or doing things with it that weren't originally envisaged/intended: you already see this to some degree with the fairly healthy patching community that has built up around the UI.

The difference there is that Nemo is not a shipping product. It's not usable as-is, and as making it usable is far from interesting or entertaining work, not many people want to do it. Creating new UIs (like Glacier) and such has taken priority over doing the boring, but necessary work like keeping things building, fixing bugs and adding required functionality to applications. This is why I gave up doing Nemo in my free time back in 2013: because it felt like I was spinning my wheels in the mud virtually alone with no real benefit.

Sailfish on the other hand is already a shipping quality product. Contributing to something that is already running and useful attracts a completely different demographic than a project that has hundreds of thousands of LOC but can hardly make a phonecall, say.