Talk to me about the Canon R50, please

I came across the R50 with an AOI housing for what seems to be a bit of a steal deal as I was looking at some versatile & budget friendly choices for a friend. Backscatter's AOI R50 housing

She currently uses a TG6 for snorkeling and diving, but has an older Canon dslr that she definitely does not want to house (she says it can be too slow to focus and doesn't like the video); the only lens she has that would uw suitable is an old canon 100mm macro.

What are the downsides of the R50? She loves garden bugs, birds & horses on land but underwater likes a bit of everything, rarely dedicating a dive to something specific unless it's like on holiday with the manta night dive in Hawaii or similar.

What are downsides of the AOI housing (other than being poly)? It looks like one can still pop on wet mounts for macro and wider if need be, so it should be a fairly flexible system?

As i am still dithering over my own options as I contemplate a move from a Canon 7dmkii/Nauticam with a whole bunch of lenses, ports & bits, I am getting a bit more confused and trying not to project too much on her quest! heck, maybe I should consider this, too 🙃

Originally budget was "what's the best I can get to get started for about 4-5 grand USD" but coming in with the gear at a nice fraction of that would mean a whole 'nuther diving trip. Really appreciate any input.