With OEI if an aircraft is trimmed for zero side slip it will have some drag due to side loading
Why so ?
The minimum drag position is some slip neutralised by some bank
I can't recall an authoritative source which has minimum drag other than for zero slip.
the pea would show "slip"
I will take the quotes to indicate tongue-in-cheek.
If we have no aerodynamic side slip (streaming wool / Beta) why would we need any aileron?
Beyond my meagre skillset to come up with a convincing two line answer.
However, I refer you to any of the standard references which will take you into headache territory with explanations as to what is going on. You might, for instance, have a read of the
USAF FT OEI Good Guts Words.