Limited room how. When setting up a track bike, you need to make sure the rear wheel can slide forward about 1/4" minimum so the chain can be derailed. I prefer more room to work, so my bikes usually have 1/2" or more to move forward, so I've never had any issues changing wheels easily.

Also, whether by design or accident, the rear wheel can spin freely when fully forward in the slot, so if I hold the bike vertical, resting on a "tripod" of the turned front wheel and handlebar, it's very easy to spin the chain onto or off the chainring.

BTW - I might add that I'm impressed by the various issues and workarounds that many fixie riders seem to deal with. BITD when we weren't so bright, we simply pulled our wheels back, tightened them, them rode without worry until a flat or need to change a sprocket made us remove them. Wheel slippage wasn't anything we dealt with because it simply didn't happen.