That's the 2nd time I've seen the 90 day number posted this week and to my surprise you guys are correct, and according to this MLB.com excerpt Miles can be optioned after the 90 days, TIL... my bad @jmomcc...
Rule 5 draft picks must remain on the drafting team's MLB active roster (26-man roster) for a minimum of 90 days during the following season to fully satisfy the requirement. While often cited as "the whole season," the specific requirement is 90 days of active service to avoid being subject to restrictions the following year. [1, 2, 3, 4]
Key details regarding Rule 5 roster requirements (as of 2026):
Initial Roster Spot: Players must be placed directly on the 26-man roster, not the minors.
Injured List Exception: If a player is placed on the MLB injured list, they must be active for at least 90 days in total to fulfill the requirement.
Returning the Player: If the player does not meet the 90-day active requirement, they must be placed on outright waivers and offered back to their original team for \(\$50,000\).
Restriction Removal: Once the 90 days are completed, the player can be optioned to the minors if they have options remaining. [1, 2, 3]