I'll leave the definitive answer to a flasker (which I'm not), but keikeis are already accostomed to growing in air. Flasked seedlings are in agar. Getting them accustomed to potting material is in the opposite direction of a keikei. Flasked seedlings are going from more surrounding material to less. Keikeis are going from less to more.

The idea of easing them both into a changed environment remains the same. But you must take into account where they're coming from. The change can't be too shocking, particularly for a younger plant. So in-between steps may be necessary for younger seedlings.

Julie