Silicone and/or its hillbilly counterpart, Pam are both used on screens while wet-on-wet priting to reduce ink build-up and subsequent print muddiness.
Many find it unnecessary with the correct inks and/or modifiers, and with high tension screens and derisively consider it a band-aid.
Then again, band-aids come in handy when the time comes.
I can't speak to Pam, but no, when used judiciously and allowed to dry for a half minute or so, silicone doesn't transfer to the shirt.