I heard there was a process for requesting additional data, but you have to actually pay for the 5 users and they’ll bump it a few TB every couple months on request. That’s from people reporting their experience with support, so it might not be totally consistent.
I kind of get it though, people hear “unlimited storage” and then don’t even make an effort to be efficient with that space, and just want to keep everything forever. There’s a real cost to that storage, and it’s higher than many think since it’s not just a single HDD like many would have sitting on their desk but a series of arrays/pools and all the related systems to ensure reliability and uptime. They probably did some calculation where 99% of users would be profitable even with their “unlimited storage” and eating it on the other 1% was a reasonable advertising cost. Over time that calculation changed and they had to update the service.
Some systems already have that. Replaced a switch yesterday and re-arranged some things on my network board and got a HomeKit notification that some things were offline and when it came back. Knowing when something goes offline isn’t as useful as keeping things up though. With something like a hardwired camera/NVR, even if your ISP service is interrupted the cameras can still record, and you can put a UPS there to keep things going, even if the rest of the network is down.