We have 15 text styles in our Design Language System and sometimes I face some situations that I have to use some other text styles instead of the existing ones. Is it weird to use some typography styles that they were not in our DLS as a defined text style?
Most style guides simply can't account for all use cases.
The decision of how and when to diverge from a style guide ultimately comes down to who is in charge and often how severe the divergence. If you are in charge, then it's your call.
I find as long as I'm sticking with defined fonts and colors, then things should be okay. It's not uncommon to break for sizing or spacing due to a specific instance. However, introducing new fonts, colors, faces, etc. may not be appropriate