This design allows the team to move the inboard end of the suspension leg to better suit the requirements it needs for the optimum set-up around each track.
Most teams do have some level of freedom in this area, but we are usually talking about millimetres rather than the many centimetres of freedom that the solution on the W15 affords Mercedes.
Tbh, I hate a lot of the direction that F1 has went in.
Banning FRIC, banning the use of exotic, lightweight materials in engines, extremely restrictive engine regulations, strange changes to rules surrounding braking systems, bans on various suspension systems (particularly ones that Mercedes used), etc.
DAS is particularly annoying. It was a clever bit of tech and was operated entirely manually, by the driver, using wheel adjustments.
It’s not like it was some driver aid where a computer did everything for the driver, like ABS or launch control would be.
This is perhaps controversial, but I think the budget cap is bad too. All it’s done is lock in advantages and heavily punished teams who make bold or incorrect design decisions.
F1 is always badged as the pinnacle of motorsport, but all these over-the-top restrictions are putting that in jeopardy.