Using Quick Start for Data Transfer from iPhone 8+ to iPhone 16

I have been watching videos about transferring data from an old iPhone to a new one (in my case an iPhone 8+ to a 16). Almost every source makes a statement about installing the latest OS before doing the transfer; the current iOS out is 18.5, but the iPhone 8+ quit receiving upgrades after iOS 16.7.11

Do they mean the latest version that your current phone can accept, or are they assuming my old phone is still new enough to accept iOS 18?

Has anyone had issues transferring data from an 8 to a 16?