Here is another example of the same issue where the adviser says the card benefits should apply...

https://thepointsguy.com/news/credit-card-free-checked-bag-points/

"If he explains the situation and provides a credit card statement to back up his story, United should be able to make a note on his reservation to add a free checked bag. There's a good chance he'll have to get some help at the airport as well, so he should make sure to show up armed with screenshots of his correspondence with United and his original credit card transaction/statement. It also wouldn't hurt to have a copy of the terms and conditions of United's free bag benefit handy, as frontline customer service agents aren't always familiar with every nuance of every policy out there."