You dropped the small detail that those new ICEs are going to replace IC and EC trains first. And those usually run below 250 km/h. And only in a later phase they are going to replace ICE 1 and ICE 2 trains, which can only go 280 km/h.. so not a huge downgrade.

They are not a replacement for those trains running fast services (with legs with 300 km/h in them).