Earlier quoted context omitted.
They run the canal at maximum capacity indefinitely. Due to the lack of downtime, any delays are in effect the same thing as a cancel from the perspective of the canal owners.
According to reports, the backlog of traffic should be cleared in about 10 days. They must have some spare capacity available in order to do that.
The canal was blocked for only 6 days. Then 10 days to clear would suggest the opposite, that there is not spare capacity. All shippers have to eat a permanent delay that will never be caught backup, everyone is 10 days behind forever.
And re-routes around Africa don't count as spare capacity for the canal itself.
Of course there may be some *literal* spare capacity, that could be realized by violating processes. But the canal is in fact run at maximum capacity according to the maximum that official process allows.