I looked at the database, and I wonder if there are not at least 2 different plants being shown in the pictures and I am not sure that either of the most occurring plants can be positively identified as O. humifusa.
This website here is a great reference for North American Opuntias: opuntiads.com
Here is the link to their O. humifusa entry. I think Lindsay's pictures look pretty close though a little on the spiny side, but that is not that big of a deal, the spines look very similar:
https://www.opuntiads.com/opun...