[jasode]

>Mathematicians use "just" with a specific meaning: it is not used to gloss over something that the author doesn't know how to explain. It has a purpose, useful for mathematically trained readers.

Based on the author's public profile, I'm not convinced the author is a mathematician writing "... is just ..." as rigorous formalizations for a math-trained audience.

Instead, the "is just" phrases are innocently slipping into explanations as a subconscious verbal tic caused by the The Curse of Knowledge. My previous comment on that phenomenon: https://news.ycombinator.com/item?id=28256522

(Also, as a sidebar followup to your comment, Wikipedia's page about homomorphism (https://en.wikipedia.org/wiki/Homomorphism) has this as the first sentence: "In algebra, a homomorphism is a structure-preserving map ..."

I'm guessing that a hypothetical edit to "a homomorphism is _just_ a structure-preserving map" -- in an attempt to add more refinement and precision to the definition... would be rejected and reverted back by other mathematicians.)