I don't think you can demand another parent do it. But if this was me in my house, yes, I'd request that phones were put somewhere safely during the party and children could retrieve them if needed to contact their parent for any reason. In fact, when my dd had her friend over the other night for a sleepover, I did exactly that, requested the friend's phone (and dd's tablet - she doesn't have a phone) before they went up the guest room to watch a film and go to bed. I returned friend's phone in the morning.
Kids should be interacting and having fun with each other at a party, not with their heads in a phone. Dd has a friend (same friend as above) who is constantly on her phone. I mean like facetiming dd and messaging at 3am. They're both 10. Dd doesn't have a phone, but she does have an ipad, which she is only allowed for periods of time every few days. Hence I notice the messages and missed calls, like all 50 of them, at all hours from this friend when I give her ipad to her to use. Same friend also has a Tiktok account with fairly suggestive posts - again, they're 10! - which I've seen because she gave dd the login details and dd downloaded Tiktok, which she then told us about and I looked through it all (before deleting it because dd is not allowed Tiktok!). The friend is followed by her mum on her account, and her older sister and other family members, so clearly they are also seeing what she is posting, which is worrying frankly.
But it was a stark reminder that this is the junk that 10 year olds will be doing (thirsty photos and all) if they are not properly supervised with tech. It's not going to happen on my watch and certainly not on my wifi, if they posting inappropriate things. Kids should be kids. At the very least, as parents we can enforce that when children are in our care. Dd doesn't have a phone, but I'd have no problem with another parent making her put it away during a party.