`motionTestValues` modifier must only expose semantics when enabled

Before, motionTestValues always exposed a semantic node, even though
no semantics were applied. This could still break e2e tests, as the
semantic tree changed

Flag: EXEMPT Test only
Bug: 415115880
Test: Unit tests
Change-Id: Idd27aa26bb87b7dc7ee7b3a869e6e7bae11528fe
2 files changed