Just a guess, maybe the high plateau of torque at medium rpm has been capped in the manual version to protect the gearbox, and the maximum power is the same for automatic and manual at the higher rpm range. There the torque is lower and also the same for both versions but there is no more danger for the manual gearbox.
In addition perhaps with the manual box the same HP is realized at slightly higher revs with a little less torque.
I was going to suggest it didn't make sense for BMW to supply an engine and manual transmission package that wouldn't take to the full torque of their 190kW variant of the B48 engine. However having had a closer look at the other cars that use that engine variant it appears they all use the ZF 8HP auto box, excepting hybrids.
I wonder therefore if the situation was as you suggest. Maybe MMC feeling they needed to offer a manual option to satisfy cutomer demand on their +4 replacement, asked BMW to provide a manual engine transmission package. Pure speculation but possibly BMW's response was to offer a gearbox from a less powerful variant that required re-programming of the powertrain to limit torque down from the standard 295lbft (400Nm) to 258lbft (350Nm), a surprisingly large reduction IMO, and one of the first things I noticed when the Plus Four was first announced, reflected by the slower 0-100 kph figure.
Would be interested to hear if anyone knows any different on this issue.
