Oh no it's definitely possible to walk (or take the buggy) to use spa and other facilities. The villas themselves are separated but it's all WITHIN the villa compound.
What's curious is that Revivo ITSELF is separated - because it's two villas (or is it three? I thought it was three villas but might be mistaken) - it's not a single compound within the villa compound, it's quite literally two/three SEPARATE villas within the complex, with no internal link (obviously). So depending on which villa you are in and what facilities you are using, you may have to use the buggy and cross through the main Aman villas compound to get to your next Revivo facility.

It's a strange location IMO for the concept (healing/wellness - would definitely have picked somewhere a bit more remote I suppose for what they are trying to achieve and not middle of Nusa Dua - allows for convenience though I suppose) and also doesn't have beach access as I recall, and similarly doesn't have ocean views either, but at the same time if anyone is looking for Aman-designed villas at a great price, it's always an option! You don't have to participate in a wellness/healing retreat progrmame to stay there (though they prefer you do/encourage it).