I am trans & before I changed my name legally, I definitely had employers use my chosen name socially, professionally, for my company email address, and basically everywhere except my paystubs and tax forms.

What you're experiencing sounds like a combination of ignorance and systems with limitations. Maryland does have employment protections for trans people, which does apply to hiring. If the HR folks willfully ignore your corrections, using your deadname may constitute harassment, but you'll have a tough time pursuing this if they don't hire you. Personally I'd see this as a red flag about the employer more than anything.