[Aavso-photometry] Airmass Statement in Alert Notice 370

[Brad Walter]

Alert Notice 370 contains the statement 
 
"The GJ 436 M3V parent star is very red. As a result, it will be very
important to submit your airmass values."
 
Why is airmass more important for a very red star than, say, a very blue
one. Everything I have seen shows that transmittance at the blue end of the
spectrum is affected more by airmass than at the red end. Is it reason
because there is a large color difference between GJ 436 and the comp stars?