Tabler never existed because his performance with the bases loaded defied the laws of physics. If he did exist, his biomechanical capabilities exceeded those of humans. I believe he was a time-traveling cyborg, but since time travel is impossible, he did not exist. his records are a figment of human imagination.
Tabler may also have been one of those guys pitchers were not willing to pitch carefully to in bases loaded situations because he rarely homered.
[edit - he walked 11 times in 109 PAs with the bases loaded, but hit 2 HRs. I have not looked it up, but i'll guess most of those BBs were in the 2d half of his career once he established a reputation for delivering with the bases loaded. He had 108 RBI in those PAs despite a .489 BA (.505 OBP). His ISO was .204, so it was not that he was completely a light weight. 2 HRs, 6 2Bs, 3 3Bs. There are a lot of guys who get RBIs = 80% of PAs in bases loaded situations with BAs .150 lower than Tabler because they were more more powerful hitters, like Pudge, Raul Ibanez and Paul Konerko. That said, an RBI per PA is quite impressive.