You might then say, "but I can still get takeoff torque with the separator open!". I would then say, "not always".
Then I would say "then why does it have in the excerpt shown by FCP say increase TO distance by 3%?"
It does not mention temperature, either ambient or ITT. If 'not always' then why a blanket 3%
A head scratcher for me too this one. If it was an ITT / OAT combo then it wouldn't always be 3% - TO distance would increase as a variable of the ITT limited power output.
UTD - just read yours. Can't think of any other reason, sounds plausible to me