This issue is indeed trivial, but I don't know how, in general, we are going to achieve mutual understanding without establishing an agreed-upon semantics.

It's not possible to fix a particular semantics outside a particular time and context, and certainly not possible to do so in general.

Here, as soon as someone recognizes that the amount of energy cited is way higher or lower than would be implied by their own definition, they should 1) identify the difference ("Boil here means 'boil n kettles dry' rather than 'bring n kettles to boil'") and 2) in most cases, avoid the wasted debate by adopting the other person's language if further conversation using the concept is needed.

Indeed - so it is clear what one should do here, which is to begin by assuming the author is adopting a well-established meaning within the relevant context. For this, we have a couple of clues: one is British English usage, given that this is a press release from a British laboratory, and the other is that there is a meaning in which the calculation works out correctly.

In the light of this, what is your objection to my comment? As far as I can tell, it is in conformance with your numbered principles.

Saying "X is indisputably the accepted and intended meaning of the phrase wherever English is spoken" is not in conformance with those principles at all.

There appears to be a certain irony in how, in your rather sanctimonious posts here, you seem to have generally failed to act in accordance with the very principles that you accuse me of violating.