Somewhat agree and disagree. I bucket people's style into two camps, stressing over the former is largely unproductive, but stressing over the latter is crucial to writing high-quality, maintainable software.
Someone's style can be "different" without being "bad", and you have two basic options to deal with it. One is to authoritatively remove the soul via process (auto-formatters, code review, and to a lesser degree linters, etc. are all designed to create uniformity at the cost of individuality.) The other is to suck it up and deal with it, as this is just an inevitability of creating a team size larger than one: people have different tastes and those have to be reconciled. I somewhat prefer allowing for individuality, and individuals should endeavor to match the style of whatever module they're working in, out of courtesy to its owners/stakeholders if nothing else. However I have only worked independently or on small teams. Most large teams (/ open source projects) have gone the former route of automating all the fun/craftsmanship out of their systems, and even I think that makes sense at a certain scale.
Someone's style can just be objectively "bad", however, and I usually find it's evidence they just don't care about the source artifact that much, and they're focused on the results. (It can also be a sign of an under-performer that spends so much mental capacity just getting the code to work that they have no spare cycles to spend thinking about matters of taste.) If it compiles / works / passes the test-suite that's "good enough" and "their job is done" and they move on to the next task. These people tend to be hyper-literal thinkers that are very micro-task oriented: they see implementing a new feature as a checklist to be conquered, rather than being systems-level thinkers on a journey of discovery & understanding.
If the author is talking about the latter, I have to agree with you that the latter are quite difficult for me to work with; particularly since I know that the source has to be maintained & supported over a much larger time-scale. The source-code is like your house, you live in it, being comfortable to work with/in/on it is the key to success. The deployed artifact may live for only a few weeks, days, or even hours before it gets replaced. The source has evolved over decades. You (the organization) are practically married to it. To further the analogy: I don't mind if somebody wants to hang posters in their room for a band I don't like. (Hell I can even handle if a group of those posters are tastefully hung out-of-level to make some kind of statement.) I do mind if their furniture is blocking a vent, the outlet covers are hanging off, there's a hole in one of the walls, a light has been burnt out for months, and the window-blinds over there are clearly broken but they insist it's fine because daylight still gets through.