Recommendation: ARIA2: Identifying a required field with the aria-required property is removed as a sufficient technique for SC 3.3.3, and added to SC 3.3.2.
As a second recommendation, ARIA21 should be added to 3.3.3.
Rationale:
SC 3.3.3 Error Suggestions is concerned with responding to a detected error in a user form interaction, while SC 3.3.2 Labels or Instructions covers providing guidance when content needs user input.

ARIA2: Identifying a required field with the aria-required property is more appropriate as a label or instruction technique to guide user input than as a technique only to be used in response to an error, which is what is currently implied (unless it is the WG's position that aria-required should only be set to true after a user has failed to fill in a required field).
For 3.3.3, a better aria technique to include would be ARIA21: Using Aria-Invalid to Indicate An Error Field.