Its making it so you cant make and keep super buffed pegasi using twin universes. Dive increases attack but not base attack, so the tu'd one has higher attack but not base attack. So before, for example you could take a 6/6 pegasus, dive it, tu it, and have a 12/6 pegasus (still 6 base attack), tu it next turn and dive it to 24, tu again, and have a new pegasus at 24/6 (still 6/6 base). Now, it will reset after one attack rather than staying that way. Anti matter also doesnt effect the base attack, so after diving a AM'd pegasus it resets to base attack.