Honey has a lower glycemic index/insulin response than sucrose.

It's a bit better than sugar, yes, and I suppose you would tend to eat less honey than sugar.

Jaggery though... I can't imagine it has a GI much different from sugar?

I think it's not just about GI, jaggery would have more GI, I am not sure, but you could think of another angle - jaggery is unrefined sugar retaining the dietary fibre - that could result in a lower GI also some other benefits which we might be still discovering.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2730183

but it occupies liver with processing fructose which iirc is disruptive to ketone production and does maintain a level of blood sugar that prevents body from entering ketosis.

If you’re purposefully consuming normal levels of carbohydrates you’re not going to be in ketosis anyways. Unless you’re maintaining a ketogenic diet there’s no reason to worry about your glycosis/ketosis state after a meal. A teaspoon of honey isn’t going to ruin your body. Likewise, if you’re over indulging it doesn’t matter much if it’s “better” sugar or “worse” sugar. I’m willing to bet the poster isn’t drinking a honey sweetened soda.

Therefore you cannot look at each component in isolation.