julia.endo said:

My experience ordering cross-border ordering internationally: I've ordered from a UK pharmacy.

I read this differently from julia.endo, on substance rather than tone. Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions. What is a personal-import allowance in one country is a controlled-import offence in another.

The figures, for anyone assembling their own picture. Keep the original post as written when you update it, and add the correction underneath. An edited-away mistake is invisible to the next person who makes it.

BethLabQueen said:

Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions.

There is a second half to this that has not been said yet. There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

I would rather be corrected than agreed with, if it comes to it.

A narrower follow-up, since the general answer is now clear:

How would you tell the difference between that and the alternative explanation?

OP back with an update, since a thread like this is useless without one.

Update: the thing I was blaming turned out not to be the cause. Leaving the original post as written rather than editing it, so the mistake stays visible for whoever searches this next.