A restorative sleep is 1.5hr+ and some would stay in the room re-settling from the 20 min for a further 45 min or an hour so LO is being shown it is sleep time, there is an example of Tracy doing this with (I think it was) 3 month old during sleep training. After the nap time (half of which was A time) she then kept baby up for all the A time, so the resultant A time was monster, then took baby for the next nap where he totally refused to sleep, taking ages to PD and eventually crashed, he was then woken after 45 mins because E was due. It sounds extreme and hard hard work, and I don't some across many here do that (but some do). However it's the sort of thing that gets a routine in place in a number of days rather than weeks and weeks of tweaks.
Then there is the other gang (like me) who would rather stab yourself in the eye with a ball point pen if you have to sit in a darkened room shush/patting for one more minute. In those cases it just isn't worth it and I then agree with your DH to just get up and get on with the day, get out the house for some air, a walk, a stretch, some sun if possible. Does everyone good IMO.
So the thing is, it's down to your choice for your family. If you want to push it and DH doesn't or feels he can't then personally I think it's better to accept his wish not to go that route. You can't really force another person to go through ST if they aren't up for it, it can build rather a lot of strong emotion and mostly not good. So either do it yourself (only if YOU have enough strength for it) or accept that right now there are short naps and just do your best to keep everyone happy and healthy yk.
x