It's not pedantry, it's wilfully not understanding how international agreements work. Taking slices of text in isolation without the entire framework of how and why they were put in place.Pedantically speaking, @Roar87 is correct here: there is no formal treaty obligation on the UK (or US, etc.) to defend Ukraine. The "guarantees" given were more guidelines than rules; they provide a solid justification for the UK getting involved (if we needed another one) but they do not, in the strictest sense, oblige our response.
Take NATO article 5 that everyone talks about, if you want to be pedantic even if it is invoked no country has to do anything to aid a member that is attacked because it doesn't explicitly state it.
It's not a computer game where if a friendly nation is attacked, swords are automatically placed on enemy icons because you clicked OK to an alliance, nor are they heavily detailed 10000-page contracts spelling out every detail.