Yep. When it comes to Wrest/Tact, the opponent's skill must be within 25.0 points of your pet's skill. For Anatomy, any successful hit can trigger a gain, so the easier the opponent is to land hits on, the faster the gains. Gregorio is perfect for Anatomy gains, since he has low Fencing/Wresting (when disarmed) skill, and is invulnerable to damage (unless you're on a specific quest).
Chiv+AI Ossein Rams are particularly nasty with how the increased melee damage granted by Chiv synergizes with their innate Life Leech ability.