I'm thinking that person must be thinking about the first "sync" or "dump" to the cloud, where someone could easily have multiple TBs of files. However, I'm guessing they think Xfinity's cap counts at all times and not necessarily realizing that doing the first big upload/dump to cloud at home (locally) won't even use 1 Byte of it.
But even if they know this and are creating or consuming more than 1.2TB of data "on the go", the likely much better solution for them than using any kind of cloud service is a portable drive. There are pocketable 5TB drives for < $100 or even faster 8TB m.2 in a tiny iPod-like case for less than $1K. If me and I had that much need to move huge data > 1.2TB every month, I'd be on those trains vs. leaning on cloud options.
And If I worried about the security of the portable drive, I'd either carry TWO+ of them (mirroring each other) and/or synch chunks of that data back to home store via an ethernet connection to minimize the throttling pains. For instance, when traveling, connect in the hotel room (ethernet) each night (or when I can) and ship a big block of more important data home.
And if I was too remote for any ethernet option at all, I might have 5 or 6 such drives along, mirror files as I go and then drop one off at DTS/FEDEX/Mail at points during the trip to ship each drive back. Even if 1 or 2 didn't make it, it's unlikely that all wouldn't make it. And each one in the latter pool would have all of the newly-created data that were shipped on the earlier drives.
If I get home with that final drive, I could just dump all of the "new" to my Synology without involving Xfinity at all, then clear all of my "on the road" drives to be ready to capture >1.2TB again next month or next trip.