No, it's not.
A boundary is something you're saying about your behavior. "If you use racist language at me, I will have to end this conversation."
And much, much worse than someone with "a minefield full of unnecessary boundaries" is someone who has boundaries they don't tell you about.
You should only set boundaries that are real boundaries for you, not just whims or arbitrary decisions. But if you do have boundaries—and everyone does; if you think you don't, then you just haven't had someone cross them (or haven't realized that's what happened when they did)—you must communicate them in contexts where there's a real chance of them being crossed.
To do otherwise is unfair to everyone else and to yourself.
I think this falls under de-escalation, and there's lots of approaches.
Communicating boundaries, or stating if-thens, can be an escalation in some situations.
Steering the conversation/situation away works in some situations.
Non-verbal communication can work, and be more tactful: it allows an accidentally-offensive person to recognise, pull back and show support. This smoothes out conversations, and is common enough that it's expected for many.
For groups of people that use non-verbal communication less, then perhaps explicitly stating things is the only option.
But don't be surprised if non-verbal communicators interpret it as combative!
"Wow, Foo got upset quickly at me, and in front of others. [Why didn't Foo make it clearer that they were getting uncomfortable [using non-verbal methods]]".
An ultimatum says “you must do X or else I will do Y”
A boundary says “you must refrain from X or else I will do Y”.
You make a distinction without a difference. In either case, without providing for compromise or alternative mutual understanding, it is likely confounding and demanding.
Additionally, an ultimatum comes with a deadline; a boundary is indefinite (until stated otherwise).
In a sexual relationship context, that distinction could be better illustrated by:
"Don't touch me like that again without asking first, or I will break up with you"
vs
"If you don't have sex with me by the end of the week, I'll break up with you".
An ultimatum is, to most people, inherently damaging to psychological safety. A boundary is not automatically better - it can be unreasonable, unhealthy, or incompatible with the other persons needs - but unlike an ultimatum, it's not _inherently_ harmful to the relationship.
I mean...I'm a pretty easygoing guy overall. My boundaries are things like, "If you come up and scream in my face, I'll tell you to sod off." "If you punch me, I'll probably shove you back." Reasonable boundaries for other people might be "if you grab my butt, I will report you to HR", or "if you ask me to work unpaid overtime, I will refuse (and report you to HR/the NLRB)".
It seems like you think "people setting boundaries" looks like telling your coworkers things like "never ever speak to me in anything but the most respectful tones" or "if you ask me about my personal life, even the tiniest bit, I will call the police". Except in extremely unusual circumstances, "boundaries" like that are actually people being abusive of their coworkers.