Does the sport mode shift point depend on how you drive? Does it shift later in the RPM range if you really push it?
Here's why I ask. My Porsche has a Tiptronic. If I drive it easy, it shifts at relatively low RPMs. But if I really get on it, it very quickly "learns" or remaps the shift point. For example, if I drive it easy from a stop light, shift point is generally 2000 RPM, but if I floor it from a stop, shift point is 6800 RPM. If I drive it hard from 1 to 3, then back off it will hold around 3500 RPM, then when it senses I'm done finally shift into 4. It will keep that high shift point through several lights until it re-maps back to low RPM shifts.
Maybe try hammering in sport mode to see.
'15 GLA250 4Matic, white, sport package, xenons, panoramic sun roof, walnut dash, beige MB tex with heat, premium package, rear camera
'13 GLK350 4Matic (wife's),
'01 Porsche Boxster S,
1938 Chevrolet Master Town Sedan. Frame off restoration - all work done by me.