The timings I was thinking of come from a Flight Controls Harmonization Working Group draft AC (possibly some earlier doc, but they are in this at least) that can be found in the recommendation letter from TAEIG to ARAC in May 2001, on the FAA website at this link below. Delay times are discussed on page 45 of the pdf, section (e)(1)(iii) of 'Enclosure 2':
https://www.faa.gov/regulations_poli...cs-8261998.pdf
That has the 1 second for recognition, and 1 or 3 seconds for reaction statements.
I don't think that draft AC was ever formally issued - it ran into the FAA's diversion of rulemaking resources post 9/11. There is an FAA Policy (or similar document) which allows any draft doc submitted to ARAC to be used as guidance, with the usual "unless we say you can't do that" caveat of course. So it's almost as good as a 'real' AC.