There are several mid motor with a weight similar to the one of the Keyde P100 and higher performances from TQ, Fazua and Bosch but they require a specific frame so much more investment from the bike manufacturer.
The all in one approach benefit is actually also more important for the bike manufacturer than for the bike user.

Globally, Helix choose this system to offer an eHelix with minimal investment.

For the user, the most important thing is how the e-assist system behaves and this is unknown for me, I haven't seen any ebike using this system nor read any independent review of this system while the behavior of the previously mentioned mid motor system from well known manufacturers is also well known and easy to test since there are many ebikes that uses these systems.
For Helix, its almost impossible to know how the e-assist system behaves before buying one since its only sold online.
The fact that there is a torque sensor doesn't mean that it work well because the performances of this torque sensor are not specified (a good one is expensive), because its not located into the crankset and because the actual behavior of the e-assist system depend a lot of the e-assist control algorithm which is part of the proprietary knowledge of every e-assist manufacturer (there are huge differences between different mid motors manufacturers).

You are right about the claims of other ebike manufacturers who also give very optimistic range estimates. But potential customers should know that the 100km is totally out of reach if the e-assist is really activated.