Cast on Elemental Ailment Issues

Cast on Elemental Ailment shows spell echo as a recommended support gem but you can't socket it? For example, If you socket comet, you can socket zarokh's refrain as a support. If you socket comet in CoEA, you can no longer socket zarokh's refrain as a support for it nor spell echo. Yet, spell echo is still a recommended support gem.

So, is this suppose to be intentional or not?

Spell Echo: Supports Spells that affect an area around you or a target location. Supported Spells echo, causing their effects to happen again after a short delay. Cannot support Channelling skills Remote skills or skills which are Triggered.

CoEA trigger their socketed Spell Gems so it make them unable to use Spell Echo. Zarokh's Refrain have the same restriction.

As for the recommended list on CoEA it's based on Spells that linked into it + the recommended Support Gems for Meta Skills. So yeah, as Spell Echo is recommended for Comet it's also recommended when it's in CoEA even if it conflict each others.