I will add that last night while I was going through all of the different integrations I've made w/Hubitat - some on just a notional level, some actually revamping to use the POST updates - that was the only parameter that I felt was missing / required additional calls to be made in order to fully utilize the update data.
Sure, to support bi-directionality/commands externally the integration still needs to grab the supported command list (and in those cases you can just grab the units at that time as well), but for simple read-only integrations having the units in the update events would completely eliminate any additional calls needed.
Not that it matters, but I would rather give up the event description than units if we are trying to shrink the responses. But I'm sure others may disagree there. My thought is that the descriptions follow little/no structure (or at least the event text is not standardized enough to rely on 100% of the time in any case) so can't really be used as-is anyway and always require additional parsing, unless they are only being used for archiving purposes. Oh, and the event description text SHOULD be completely redundant information withe the name and value's passed in the event anyway (by definition).
A happy side note is that using the POST method significantly reduced the parsing code required externally versus drinking from the event socket fire hose, which is very welcome.