How often does CX randomly block out inventory for F?

I'm flying HKG-ORD on August 6th and I've been keeping an eye on it, and whilst the other classes have come in and out of zero inventory, F has gone from F5 A5 to F1 A1, sat like that for a week then went back to F5 A5.

Just looks all over the shop!

I have an F award waitlist in, not holding my breath given those loads but I just thought it odd that they blocked out revenue F inventory for about a week.