I started to do that because I wanted to put the tom to the left of my bass drum . but I noticed that my bass drum started to resonate more , and I sound more powerful.
after I saw the bob gatzen video , It became more clear . he said that the toms are putting pressure in the bass drum , and that dampens the sound , and also increase the tension in the shell , what raises the pitch of the drum .
try it , and see the difference