As a lowly silver I’ve noticed it work in my favour a handful of times.
2-3 times in CE I’ve noticed the seat next to me blocked in Expert Flyer a day or two before travel and it’s remained so for the flight.
Last year travelling solo, ORD > LHR in CW, the day before travel I noticed the seat next to me was showing as blocked (old CW, 2 outside seats, I’d selected the window seat). Again this remained the case during boarding. The cabin was only approximately half full.