I checked with the sw folks and we average if there are more than one temperature sources in a room (for both the displayed value in the room tile and in the algo when thats available).
My Ecobee needs to have a sensor in that room so that it can use that room's data to determine whether or not it needs to heat/cool (remember, Flair can use Ecobee sensors, but Ecobee cannot get data from a Flair Puck). This is not negotiable.
Thought I would chime in here - while we don't push data to Ecobee (and they don't grab it from us), when our automation is available, we (optionally) adjust your Ecobee based on readings from our system and theirs. If you plan to leave the Flair Ecobee Integration as 'Use Thermostat Set Point' this will prevent us from writing to the Ecobee, only allowing us to adjust vents and read data from Ecobee but I wanted to clarify if it is possible to have us write back to the Ecobee with a different set point as if it had that data available to it (I think ecobee just takes an average of their sensors).
The virtual room idea is smart thinking if you would like to remove the contribution of Puck to the aforementioned average. If you put it in a virtual room, you should also make sure that virtual room is not part of any zones.
Another way to do this is to not assign the puck to a room. If you already have it in a room, you would need to ditch that room and then when you add it back, not add the Puck. I don't recommend this simply because I haven't really tested it.
My two cents - if you have your temperature sensors covered already - eventually we will do some AV device control so you could put it in a room where you use remotes. Its not out now or anything, but its pretty easy to add in, we are just staying heads down on getting out the more core temperature related automation and other features.