One thing i am finding, and i will have to confirm is that if the bump is higher the shot does change the flavour so thats why i do a flush to reduce the hump. My hump is around 203.5-204.5F after a 4-5second flush. I wait five minutes or more for my second and follow up shots and i get consistent results (only a quick 1-2 seconds screen flush)..
It's very hard to know how much of a 'bump' the puck actually sees. The bump in the TS water that the thermometer is measuring is very much 'filtered' out by the thermal mass of the E61 & portafilter, when the water actually starts to enter the puck. In electronics, I think it would be like a capacitor smoothing out AC ripple.
One almost needs a SCACE *and* a group thermometer to see the relationship between both on their actual machine. But I'm guessing that the puck is not seeing the big bump shown on the thermometer.