Can Oracle 'Quickened Casting' feat be used on focus spells?

The text of the 10th level Oracle class feat 'Quickened Casting' says....

If your next action is to cast an oracle cantrip or an oracle spell that is at least 2 ranks lower than your highest-rank oracle spell slot, reduce the number of actions to cast it by 1 (minimum 1 action).

Focus spells are not mentioned. Does this mean focus spells cannot be quickened, or are focus spells implied to be included as a sort of cantrip?

Focus spells are always cast at your highest spell rank

I can vouch for that too.
Its safe to say that Focus Spells are still spells since there are Focus Cantrips. Witch Hexes and Bard Compositions as examples.

Focus spells are always cast at your highest spell rank

Yeah, that is the biggest problem with the interaction.

Focus spells are definitely spells and qualify for pretty much anything that just wants spells in general. There are several things that don't interact with Focus spells by specifying things like 'when you cast a spell from your spell slots'. But anything that wants 'when you cast a spell' or 'when you cast a non-Cantrip spell', Focus spells (or at least non-Cantrip Focus spells) would qualify.

But there is currently no way of casting a Focus spell at a Rank lower than your highest casting Rank. So Focus spells would not qualify for Quickened Casting because of the maximum Rank restriction.

An Oracle Focus Cantrip would qualify, but I don't think there are any Focus Cantrips from the Oracle class and Focus Cantrips picked up from an Archetype wouldn't be Oracle spells.

You could ask your GM if you can cast your Oracle Focus spells at a lower Rank so that they do qualify. That would probably be the best houserule to allow it to work.