Can subaccount holders load money?
Yes, anyone can load money to someone else's card, just like you can deposit money to someone else's bank account. For instance, one of my Redbirds is on g/f name and I load it with my credit cards. However, because Redbird is new, there are reports of some cashiers not letting you load other people's Redbirds.
Any data points on atlantic
There have been many reports of the Atlantic store in Brooklyn only taking debit cards for Redbird loads since a few days ago...try the other Targets, people have had luck with them.