Important: If you are using Timestamps Optional, then do not sets.visitorID on data that is already timestamped. This can lead to out-of-order data and negatively impact time calculations (such as time spent values), attribution (eVar persistence), visit number/visit counts, and pathing reports.
Timestamps not allowed (setting s.visitorID supported)
Timestamps required (setting s.visitorID not supported)
Timestamps optional (setting s.visitorID supported but not on timestamped hits)
What is the reason for this limitation, and is it likely that this limitation will be addressed in the near future?
No, using s.visitorID on a timestamped report suite does not change the timestamp used to generate the ordering. It is not recommended to modify s.visitorID in a timestamped report suite for this reason.
That's correct, the web data would rely on hit_time_gmt and the app data would rely on cust_hit_time. The problem arises when the s.visitorID is shared between the two data sources, meaning that there's a potential for out-of-order data being inserted into an individual user record, which will cause incorrect reporting.
Hmm... So we have a web based report suite (uses VisitorID but no timestamps), and an app based report suite (uses VisitorID and timestamps).
If using s.visitorID does not change the timestamp used to generate ordering, then if we combine these report suites into a timestamp optional report suite, wouldn't the web data rely on hit_time_gmt, and the app data would rely on cust_hit_time_gmt? That's what we want, but Adobe's documentation says the timestamped hits might come in out of order.
Does using s.visitorID on timestamped report suites force the processing to rely on hit_time_gmt rather than cust_hit_time_gmt? Depending on the answer, it may be worth it to have slightly out of order data, if it means we're able to see usage across multiple platforms by the same users.