Specifically regarding "VIN rollout" and "by VIN," someone from our Service Center asked when we purchased our Tesla and responded by saying we'll get the FSD computer later than those purchased earlier when the mass retrofit begins, so while they didn't specifically ask about VIN, the response matches up with the preference to begin with lower VINs then move on to higher VINs, i.e., giving preference to those who have waited longer.
Otherwise thinking of "VIN rollout" as just a general targeting of who gets the retrofit instead of a comment on which vehicles get upgrades earlier, the message could have said "we'll do upgrades for those who need upgrades" but that's somewhat obvious. The repeated "by VIN" statement seems likely to be more than "the obvious."