We passed around candies in microbiology. Some had been inoculated with Serratia marcescens. After some passing and handshaking, a sterile swab wetted with sterile saline was used to swab the palms of the participants and swabbed onto agar plates. Serratia marcescens produces a red pigment, so it was easy to spot the colonies. The exercise was intended as a little practical exercise in epidemiology. It worked fine. I'm pretty certain nobody played with the candy for anywhere near 30 seconds. The bacteria was passed along fairly efficiently.
RE: the 30 second rule -there was nothing in the link you posted about transferring bacteria from someone’s hand that is contaminated with fecal matter.
Floors are probably cleaner and drier.Bacteria probably die ,or at least become dormant, on a hard ,dry surface.Maybe the grad students could test this premise;it is likely to be more useful than many college projects.
My rule is: Don’t hand me any of your ****!