The particular Cal-Hypo you are using may have more calcium hydroxide in it which is analogous to the excess lye (sodium hydroxide) in bleach so that could account for the faster rise in pH. The higher amount of calcium hydroxide might not be related to the Cal-Hypo strength and is probably more related to the manufacturing process so a different brand/manufacturer might give you better results. Most Cal-Hypo brands have a pH of a 1% solution around 10.4 to 10.8 which is somewhat lower than that of Clorox Bleach (when adjusting for concentrations) -- if you can find an MSDS for your Cal-Hypo and if it says the pH is higher than 11.0 (say 11.5 or higher), then that could explain what you are seeing.

Some of your pH rise, especially from a pH of 7.2 to 7.5 or 7.6, is probably due to your TA level as well as the aeration from the spill-over from the spa, but that would have also occurred when you were using bleach.