That is possible, but there is an elevator to all 3 floors so I don't know why her arthritis would have hindered her in not going down to the basement level. I think there just wasn't a need for her to go down there. Everything she needed with the exception of the pool and sauna were available on the other floors.
If she parked in the garage regularly then she would just open the door to the home, turned left and head up the elevator. No need to go to the wing that the pool is at.
I agree, the Sherman's didn't seem to make use of the pool based on statements from their cleaning lady. It was also stated that Honey always parked on the right side of the house to an entrance which led down a hall and eventually into the kitchen. That was were her car was parked that night. I think it was Frank D'Angelo who said that Barry always parked his car at the front door, because "he was too lazy" to park it in the garage.
His statement about Barry's parking habits is something I find very relevant, as I've said before. Just as Honey usually did not use the garage, and Barry was known not to usually use it, I have to wonder why Barry switched his usual habit, and went to the garage that night. (the weather report didn't warn about significant snow accumulation, and Honey wasn't concerned). There is no video surveillance in front of the Sherman's house, that we know of, and TPS seem to only have video of the night walker that doesn't show him actually close to entering, or leaving the Sherman property. I suspect that there is no video of BS initially parking his car at the front of the house either, and if he was confronted.
If Barry was confronted as he parked his car at the front of the house, and was forced to drive to the garage, that might suggest that more than one killer was involved. How could one perp know exactly when BS was coming home, and that he would park in the garage instead of in front of the house? It seems obvious that BS was attacked as soon as he entered the house from the garage (gloves and house documents dropped on the floor). Someone inside the house or possibly in the car with Barry could act that quickly.
Yet there is only one suspect per TPS after all these years...the night walker, who neighbours couldn't identify, and therefore he shouldn't have been in the area around the time of the murders. That''s It?! Greenspan's investigation resulted in finding that it was likely that more than one hired killers was involved. If TPS don't have video of people entering or leaving the Sherman house, I guess we will never know.