Maybe backlog will be cleared as result of some ships taking route around Africa?

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.