I know I'm known for being overly conservative. But could you please flip them back? You can flip the techs they unlock for all I care but the Garden have always been the Garden, randomly changing it is going to make new people feel even more alienated.
Also, your logic for Baths needing access to water and Gardens not is kinda flawed, Gardens need plenty of water.
If this really is a tick for you, replace the Bath with something else, just leave the garden alone.
This isn't about something being good or not, it's about it looking boring.
For the Kuna, the improvement alone is super-restrictive, you need forests/jungle and you can't build them next to each other. That might not sound like much, but it is actually really restrictive.
I'm not opposed to modifying the Kuna's yields later, but the +2 science was overperforming.
Re: Baths/Gardens, it is more that just a water issue, it was a matter of benefit (wells come earlier, benefiting non-freshwater cities, thus baths - coming earlier than gardens - needed to benefit river cities for balance). It wasn't a change for change's sake, it was a balance choice.