Prepare for your new iPhone - iCloud Backup and temporary extra storage - what is this exactly?

I preordered a new iPhone last week and today I received a message in settings to prepare for my new iPhone. The support article was helpful but I still have a couple of questions.

This particular message said that Apple will give me additional temporary space to back up everything, which seems odd because I already have automatic iCloud backup of everything enabled (all apps, photos, messages, etc.).

Does anyone know what the difference is with this particular backup versus my automatic iCloud backups, and will this new backup keep everything up-to-date until I receive my new phone later this week?

Since my new iPhone doesn’t arrive for another few days, I want to ensure between now and then, that everything will be the most recent. I can tell it is backing up a lot of information given the hours it has taken so far, so maybe this is different from a regular iCloud automatic backup but I’d really like confirmation.

Notes: upgrading from iPhone 12 Pro to iPhone 14 Pro; currently have 200GB iCloud storage plan with roughly 50GB remaining