I’m not an electrical engineer but I did work with explosives a little in the army. You’d only need a small amount of high explosive to do some serious damage to someone if their phone was their pocket and that explosive went off. Modern phones have plenty of empty spaces to stuff full of enough explosives to do lots of damage. It’d be a lot easier to detect then just making the Li-ion batteries ignite but who can say what the IDF can smuggle into the supply chain.