Beehive springs/retainers have less mass, (one of their advantages). That alone will minimize pushrod deflection
(pole vaulting as you call it) during an aggressive valve opening event. TI retainers help, but a
double spring is still going to have more mass than the beehive. F=MA
Then there's the issue of spring harmonics, beehives don't have a single resonant frequency, it's spread out over
a wide range to minimize harmonic "ringing". Probably not an issue on these engines, but IDK for sure.
I'm not here to convince anyone or change people's minds. Use whatever you feel comfortable with!
-MC
PS: I'm going to run it by Darin Morgan when I see him next week.