Secondary fermentation, in a "beer sense", is a bit of a misnomer.
While you can rack when it gets down low(er), by doing that, you can leave behind so much of the yeast colony, as to cause a stuck ferment, and without enough nutrition for the colony to rebuild, stuck it stays.....
Equally, some will do that to.remove fruit or spices (whole ones). Yet they'll stir up any lees and then just strain off fruit/spices, but moving the liquid.
Needs a smaller container if you have finished the main ferment to allow for racking loses.
Some will just finish in a bucket, doing most of the production processes, then rack to.glass for s final racking/clearing, so they can see what's happening.
Your only proviso being, that once the ferment is complete and any possible beneficial CO2 layer has been dispelled, minimum airspace is needed for aging, plus glass is necessary as it's completely impermeable to air/O2.
Mead, especially traditionals, doesn't oxidize quickly like beers, or wines with a fruit element, but it can with time........
Meads have a lot more leeway in the making stage, so it's more your choice.
Why not make in the bucket, then split it down for the finishing ?