And yet others have pointed out it is possible.
The return times aren’t given out linearly from early to late. They fluctuate through the day for all rides except the few like Slinky and Jungle Cruise which do tend to sell out early on. But rides like Big Thunder, Splash, Space Mtn, Pirates, HM, ToT, RnR, TSMM and others can all be stacked for a nice afternoon / evening of 4-5 rides. I get envious reading their trip reports.
Not on the day I visited HS. For MK, yes, you can stack and get decent PM options.
In HS, Slinky was sold out in less than 5minutes. By 11am, there wasn't much left in HS. I could get a pass for Muppets, but I would not get in to see Muppets any faster than we did without a G+ for Muppets. That is the type of G+ pass that is available after 11am.
I also want to stress again- LOOKING at G+ options and BUYING (Selecting) G+ options are two very different things. Data collectors are mostly not BUYING passes when they collect availability data, because that costs $. (At least I don't think they are.) They would need a park ticket, a park reservation and $15/day on top of that, and even with all of that, they could only book 1 pass every two hours. I don't think they are spending that kind of $ to collect data.
Before my visit, I also watched G+ availability. When we actually selected our G+ the time we actually get was often different, especially in the morning, and especially if you choose a high demand G+. If you choose a low demand G+ pass, like teacups, then you will probably get the time you picked.
On one of our MK days, I wasn't going to book G+, but we changed our plans. I started book passes about 11am, and we still would up with -I think 5 G+ passes. I think we had Space Mtn, Buzz, Pooh, and Splash (during the fireworks). From Splash, we made it to HM, which had a short standby at that hour. I'm not 100% sure what #5 was, but I think it was either LM or Aladdin (not much of a time saver). Considering we started so late, that was still pretty decent. I recall doing the trio of Space-Buzz-Pooh, back-to-back with G+ passes.
Then again...the last time I went to MK pre-pandemic, we had a long string of FP in MK that was pretty crazy.