It's about exposure in general, not just food. The Disneyland sign is likely because they use gasoline engines in various places - same reason as parking garages. Might also be from sand in kid play areas or anything involving dust.
Ooooh so that is the reason of all the crazy Cancer warnings that I see in California when I go. I remember at some point while boarding an airplane in California that I saw some cancer sign in the worm-aisle (what's the name in English?) that you pass while boarding
fries - completely ok: a lot of people get in contact with them, but putting sign on them while not putting warning over any other harmfully (over)fried products seem at least illogical(yea, creating regulations doesnt work in us, or at least there's no efficient mechanism, but still)
sand - widespread construction material, i wonder why they only put label regarding cancer instead of placing usage restriction over maximum allowed radiation flux produced from square meter area of material(some decorative stones would not fit into safe range but are ok for a lifetime risk of any person)
* Parking garages
* French fries - https://www.snopes.com/fact-check/mcdonalds-acrylamide-warni... (This sign is real; the McDonald's by my house has one)
* Toast
* Seaweed
* Coffee has been a battleground: https://www.consumerproductslawblog.com/2019/06/what-now-cal...
* Sand
You would be hard pressed to find something that prop 65 does not require to be labelled as cancer causing.