So (if we take your interpretation at face value) you could call it a 'presidential power grab', or maybe even an 'executive power grab' (if we stretch things and assume power is being transferred away from executive departments subject to greater oversight), but 'federal power grab' still doesn't make sense. No power is being grabbed from or by the federal government as an entity.

For that matter, those agencies report to the president anyway. So this is more of a reorganization than a power grab.