Nasher
I think he means the tyres have been stored off the rims and stacked up.
Tyres that have been left like this for some time can be an absolute bugger to get back on the rims if theyre tubeless, as you cant get the beads to pop up onto the rim, because the tyre is out of shape and the beads wont both seal at the same time.
The usual trick is to use either a woofer as we used to call it which was a big air tank with a gate valve and nozzle, you can get a lot of air in the tyre quickly with one of these to pop it on the rim, (through the open bead)
or squirt some easy start in the tyre and set lite to it, The rapid expansion literaly blows the tyre on the rim

Usually its not a problem once theyve been stretched on a rim for a while they regain their shape especially if they have done a mile or two.