When something uses your total level, it says so
The rules on Multiclassing include the following:
The experience point cost to gain a level is always based on your total character level, as shown in the Character Advancement table, not your level in a particular class. [...]
Your proficiency bonus is always based on your total character level, not your ...
It's paladin levels
For these reasons:
The rules are written assuming only single class characters except when explicitly dealing with multiclassing.
There are vanishingly few features that use character level rather than class level. Off the cuff, Cantrip scaling and proficiency bonus are the only ones I can think of. It is explicit that they use ...