Neither of them mentioned eternal scoreboard, OR the fact aggy would have to dominate the series for quite a while just to draw even on the W/L, much less take the overall lead.
TBH these are irrelevant or reason's Texas avoids playing A&M
The idea is that it's not that either of them have outright shown fear of each other. It's more so that they don't want to risk the perceived advantages they have by playing each other.
Just because Texas hasn't said no doesn't mean that they are willing to face them. As Joe said, both the AD's have each other's numbers. Both would probably get the game going, but neither want to. The reason being both are fine with the perceived advantages they have (whether they are justifiable or not).
Texas is scared of playing A&M not because they are afraid of A&M itself, but they fear the fact that if they lose then A&M can say they're not what they were in the Big 12 anymore, it's a new era, blah blah blah, and they'll have the result on the field to prove it. Then Texas loses recruiting ground, loses eternal scoreboard, and has a whole bunch of angry fans.
Texas A&M is scared of Texas for a similar reason. The perception that comes if they lose. They can tell themselves all they want that they are not living in the shadow of Texas and that they are equal because there is no game to prove that they are potentially lesser. If there was a game Texas A&M loses the ability to say this. They'd lose face, lose recruiting ground, and also have a bunch of angry fans.
Simply put, it's too risky for both the schools to really want to play each other. No really that they're scared of each other, but they are 110% fine avoiding playing each other.