In my experience (so not an opinion), the addition of a ZWB2 filter to 365nm light from any current UV led improves the fluorescence contrast enormously, allowing users to distinguish many fluorescence details that are completely invisible without the filter. Further, the stray light from a UV-led is a particularly poor source for background illumination, if a background illumination is desired, a second white led would give better quality plus there is the option to switch it off. Or the inbuild smartphone light could be used as secondary illumination. It does complicate the design of course.

This is all a suggestion from my side to improve the design, I do not mean to say that the current design is bad, I still think it is a nice gadget as it is now.