The FAs might not be pulling out calculators, but it's possible that someone further up the chain did and (unofficially) passed down direction/guidance on this (deniably, of course, to CYA with the regulators). It is NOT unheard-of for FAs to know who has tight connections (in F on DL once I had the FA come by my seat and tell me "Your connection will be at this gate"; going that extra mile does happen), and it is also possible that the pax had raised the connection issue with the FA earlier in the flight.