I agree that there's something manual going on. Someone is clearly pressing a button saying "collected". I know that when they do come to me, they tend to come at 10am-ish - I actually often see the van in nearby streets, including yesterday when they didn't show up.
Yesterday the fake "collected" email came at 2pm-ish, still within the window they'd offered. But when the email came I knew what was going to happen, and made the 15-mile round trip to the PO. While I was out my neighbour texted to say the normal postman, who doesn't do the collections, had arrived to collect it! The time was a bout 20 mins outside the agreed window, and 50 mins after the "collected" email.
Last time I got the fake "collected" email I waited in case they came; this time I didn't wait and ... sod's law!