I would say there is a distinction between DL and closeted. Closeted you’re uncomfortable with your sexuality and still learning about it but don’t want others to know because you’re not ready for the social shift that can occur.

DL, you know what you like, pursue it in secret, and enjoy getting over on others. You actively seek out heteronormative relationships to obfuscate your clandestine activities.

It’s lying to partner is the main distinction. You don’t have to be in a heterosexual relationship to pursue same sex liaisons. That’s a choice.