That's only for opponents coming toward him since when you're moving forward your vision is more limited as your head leans in as opposed to leaning back giving you a broader vision. Not only is your vision less but the time and space you give to Pac while moving in is also cut shorter making the landing of those off angle punches by Pac far easier. And since he fought mostly brawlers or guys who acted like brawlers (Cotto etc) it's the main reason he's ended up the favorable results he's had.