Oil spaced & Air spaced

Why would an Oil spaced triplet using FPL-53 exhibit a slight amount of CA, while an air spaced triplet using OK-4 does not?

I've been considering a TEC 140 which gets excellent reviews, but am very curious about this.

The air spaces allow the designer two more
surfaces to "play with" for adjustment of
aberrations. But the extra air-glass surfaces also
require more careful figuring of the glass and
more sufaces to be coated, so it may cost more $.
It also depends on what glasses are chosen for the
other elements -- just having FPL-53 or OK-4 does
not make the lens.

"Why would an Oil spaced triplet using FPL-53 exhibit a slight amount of CA, while an air spaced triplet using OK-4 does not?"

Were you comparing two 140 F/7 lenses one oil spaced and the other air spaced?

Vahe