Abstractions are drawn along different axes in both OOP and FP.

The showcase example "Circle, Square, Rectangles are kinds of Shapes that have area" represents an abstraction that is present in the conceptual schema (aka Domain Model, aka Universe of Discourse, aka "problem space"), regardless of implementation style.

Likewise, what you call "mathematical abstraction" (and I'd prefer to call a "implementation model") is present both in OOP (eg "visitor pattern, inheritance, facade") and in FP (eg "fold, pattern match, monad"). I don't really think the difficulty in groking "visitor" is much different from groking "fold".