Not all wrestling mats are designed to have the same amount of spring, do they?
No, they are not. The ring we trained in had much more give than the one the promoter used in shows. I remember a local promoter had one even "softer." Some Indy promoters, though, would use old boxing rings that they no doubt got for a good deal. Boxing rings are f*cking hard, dude!
A lot of it has to do with the number of cross beams that run under the platform, as well as how far apart they're spaced. More beams closer together results in greater rigidity. Fewer beams with greater spacing has the opposite effect.
When WWF signed their original deal with NBC to do
Saturday Night's Main Event in the 80's, the network insisted Vince stiffen his rings because it was feared the action would look too phony with the setup the Fed had been using at the time. Vince complied, and as a result, guys started getting more injuries.