The cooldown is mandatory, while setting up cross-save you set Steam as your active profile making your Epic data dormant. Once the 86 days are up, you can deactivate cross-save but this will trigger a further 90 day cooldown to be able to reactivate cross-save. Purchasing silver during the 86 days will bring it back up to 90 days. Bungie wont step in to reduce it, override it, or set your Steam as your active platform