When activating a segment to Marketing Cloud, Data Cloud requires a valid Contact Point (e.g., an email address) for each individual profile. If a unified individual in the segment does not have an associated Contact Point record with a valid email address, it will be excluded from the activation payload sent to Marketing Cloud. This is a primary reason for a discrepancy between the total segment count and the final activated count, as the activation process filters for actionable profiles.

A. Frequency capping is a feature within Marketing Cloud Journey Builder to control message volume, not a filter applied during the Data Cloud activation process itself.

C. Engagement-based suppression is a list hygiene process that occurs within Marketing Cloud, not a filter applied by Data Cloud during the activation push.

D. Data Cloud activations can and do create new subscriber records in Marketing Cloud if they do not already exist, provided they have a valid Contact Point.

1. Salesforce Help. (2024). Activate on Marketing Cloud. Section: "Prerequisites for Marketing Cloud Activation". This document outlines the necessity of mapping a Contact Point object for activation.

2. Salesforce Help. (2024). Considerations for Marketing Cloud Activation. This page details that individuals without a mapped party identifier and contact point are excluded from the activation.