Oh so true! Before I visited Japan for the first time I thought having shit left on my ass is just a normal thing. But later I also visited Morocco and they have a bucket of water on the toilet so you can wash yourself. It seems it's only in Europe/America where people don't wash themselves after pooping.
They have been disappearing in France, sadly, because people couldn't afford the space…
I'm adding integrated bidets to all our toilets in our oncoming renovation though.
I got a bidet but then I read you have to turn it off at the connection to the water (at the bottom/back of toilet) every time or eventually the gasket can wear out and it will explode and the water will just go and go and go. If that happened at night or when noone is home you'd have major water damage!! I thought you could just use it with the trigger. Do people really actually fully stop the water every time? I uninstalled mine because I don't think I can reliably remember to do that.
The T-adapter? That's not mechanically complex and should literally last forever if made out of the correct materials and isn't touched all the time. It should be no more fault prone than the connection to the toilet.
A misaligned thread or a washer not fitting quite right might be an issue from a bad install. That's an easy fix though and you should see a leak before things go catastrophic.
If your really looking for piece of mind I'm sure there are t adapters that can close themselves down in certain failure states.