Maybe the hotel worker was being extravagant; I dunno. However, I know that the Peninsula Chicago does it, because he proudly told me that was the case. We even had a brief discussion about this very topic. Also, think about it - how is the Peninsula brand able to offer 6am/10pm check-in / check-out on a regular basis, at all of its 12 properties across the world, when this is such a valuable commodity? There is no way they can offer that on a consistent, regular basis unless they either a) have an entire army of super fast, efficient cleaners, or b) are able to keep the rooms unoccupied for a day in-between guests.
I haven't stayed at the other brands all that much, but from my experience with three of the brands I mentioned above - Peninsula, Four Seasons, and Mandarin Oriental - I've never been denied a 8am-10am check-in, ever. 🤷♂️