Ideally, all prospects should post to Salesforce as soon as they're created in the Marketing Automation Platform (MAP) rather than waiting until they hit a scoring threshold. They can belong to a queue or holding user in Salesforce and then get routed to a rep once they hit the threshold.
This is for two main reasons:
Attribution Handling: The attribution handling logic lives in Salesforce, so information about how a lead entered the system can get overwritten if the record stays in the MAP.
Sales Processing Measurement: The sales process date stamping lives in Salesforce, so if some prospects are held in the MAP, we won't be able to report on the rate at which they progress to being routed or how long it takes.