As is typical at the TTC, when the St Clair route was being re-built they knew the new streetcars would be longer but did not think to make changes to to St Clair West loop to optimise operations.
At St Clair Station the unloading platform looks long enough for a Flexity, and of course the loading platform could likely take two, but there at least they could have added a storage or bypass track to have a place at least stash a streetcar, there are none west of St Clair West at all.
But some of the other stations are already worse off, with no room left to expand.