I think that 3 weeks in primary is way too short...Most meads are just finishing up active fermentation at that point, and I think you'd be better served to leave the mead in the primary container for at least that same amount of time after to allow the yeast to clean up after itself. I generally have mead largely cleared before transferring (and occasionally bottle directly from primary after 3-4 months. Most yeasts tolerate this fine, and will not cause off flavors.)
Once the mead has been in primary for 6-8 weeks, I have a pretty good idea of what it will taste like, and what the OG is, and if I'm going to transfer at that point, I will make my stabilization additions and transfer a few days later, backsweetening as it goes into secondary. In a sense, my "secondary" is already at tertiary or bulk aging status...all I have to do it let it finish clearing, including the extra protein that got added if I did backsweeten. If I get impatient and/or need the carboy, all I have to do is add finings and I'm ready to bottle.
I've yet to have anyone present me with any definitive evidence of this, but yes, the party line is that bulk aging will result in a more consistent mead than bottle aging. I think this may be a bunch of hooey, but I have no proof either, other than that I've never cracked open a bottle of my mead and said, "gee this is really different than the last bottle"......