Not an Epic engineer, but choosing centimetres as the base unit affords more precision on smaller scale things such as character animations.
It’s worth noting that the engine does have support for tagging properties with a unit type in C++, and there is an editor preference for changing the preferred display units based on the property unit metadata. This isn’t widely used in the engine though, iirc.
It’s also worth noting that in UE5 there is the Large World Coordinates functionally which changes all types relating to position from single to double precision. This is enabled by default in UE5 afaik. So using the tag stuff above means that you can make changes in your preferred unit of choice and not really have to worry about loss of precision at either the low end or the high end.