Well, I said the main parse function of this beta firmware seems to round off that value based on a short run of log entries posted by user @cscheiene here.
In those log entries, the log entries two consecutive raw temperature report parse description strings of temperature: 21.0 C, and I would be very very surprised to the exact same value reported twice in a row, because the Xiaomi sensor it came from just doesn’t work that way. But a longer run of log entries is needed to confirm whether all temperature report parse descriptions end in .0 or not.
Either way, the current firmware supplies a raw temperature report parse string with precision down to 100ths of a degree.
And I need to mention again that if I use SmartThings’ recommended method of zigbee.getEvent() to fully parse temperature reports, the values are rounded off to the nearest integer, which is why I wasn’t using that method in the first place.