Yes for sure those tartan trousers are far too low-waisted to be worn with Highland jackets.

There's an elderly gentleman piper here, now retired more or less from active participation in the piping scene, a WWII veteran of a Highland battalion, who invariably wears tartan trousers and an ordinary Argyll jacket to Highland Games and other local functions. He looks very dignified and smart in this attire. (They might even be his old regimental trews... they're in MacKenzie Seaforth tartan, and he was a Seaforth Highlander.)