“After all, a parts kit without a receiver is just so much scrap, particularly if you bury it in a load of other scrap.”
Israel was very restrictive on what got into Gaza, cement and rebar was closely controlled ( but for sure some % got taken off to build Hamas tunnels and bunkers) They would or should not have let a load scrap metal into Gaza that could be used for any purpose.
There are plenty of ways to sneak in piece parts otherwise. I was simply listing one option.