[hirako2000]

Or maybe when usage is low so that we try again.

Or maybe when usage is high they tweak a setting that use cache when it shouldn't.

For all we know they do whatever experiment the want, to demonstrate theoretical better margin, to analyse user patterns when a performance drop occur.

Given what is done in other industries which don't face an existential issue, it wouldn't surprise me some whistle blowers in a few years tell us what's been going on.