[OJFord]

It wasn't an abundance of caution, it was things (that you might previously have eaten and enjoyed as a sesame allergee) newly having non-trace amounts of sesame added deliberately, to save having to qualify the previous possible trace amount as low enough once it was recategorised.

Well-intentioned change, unintentional bad outcome for those affected.

[ethanbond]

Because they couldn’t prove safety… I.e. out of an abundance of caution.

[OJFord]

..I suppose you can read it that way if you want, but the result of something going from 'may contain trace amounts of sesame seeds' to 'definitely contains non-trivial amounts of sesame seed' is hardly a win if you're allergic to them. You at least had a choice to risk it before, or might have known it wasn't a risk because your allergy would only be triggered on a larger amount even if some did make its way in.

(And the regulators/legislators intention had been to benefit those allergic, so it's not just an unfortunate side-effect, it totally backfired.)

[ethanbond]

I'm going to go out on a limb and say that this rule change happened because people were getting hurt from sesame in unlabeled foods. So yeah, it is a bad side-effect, but it probably actually does solve the problem it was intended to: to prevent harm, not to expand food choices or even to hold the number of food options steady. It was obviously going to reduce options, it just did so much more than expected and in an unexpected manner.