yhcole--I think there are a lot of variables to consider when it comes to LOs and short naps. Some babies are chronic short nappers, some even from Day 1. They can take a few short naps during the day, are happy, and sleep well at night. For these babies, the short naps happen regardless of A times, wind downs, httj and/or w2s.
However, there are other babies who short nap because of a routine/prop issue.
There are babies who, starting around 3 months, start taking the 45 minute naps bc they have to learn how to transition through the light sleep phase of the sleep cycle. These babies usually tend to WANT to sleep longer, but just have to learn how.
It's sometimes difficult--especially between 3-6 months--to figure out what kind of napper your LO is. I like to err on the side of caution and try to extend naps either by a routine tweak, httj, or w2s. If none of those things are working, and the nights are still good, then usually LO is a chronic short napper.
You mentioned that you don't think your LO would take long naps if you weren't there to hold him. If you're referring to using httj, it can sometimes take a while for LO to learn to sleep on their own. We had to use httj for every nap for ~2 months for DS. He was the developmental 45-minute napper...and then one day, he grew out of it and started taking 1.5h naps on his own.
If your LO isn't sleeping well at night, and you think it's a nap issue, please don't hesitate to see if we can be your sounding board.
HTH a bit!