Is there a bias against mentioning your name on presentation slides?
There is nothing wrong with mentioning your own name in full in citations on your own slides, and nobody would think anything of it if you did. However, there are a number of reasons why people do this.

Replacing your own name with initials is a subtle way of emphasizing that it is your work that is being cited. You can think of it as a “humblebrag”.
Since you are usually talking about your own work, you end up citing yourself a lot. Replacing your name with initials simply saves space, especially if you have a long name.