They are similar, but not the same. DD Waiver hearings and regular Medi-Cal hearings both use an Administrative Law Judge (called ALJ for short) to decide your case.
The ALJ for DD Waiver hearings works for the Office of Administrative Hearings (OAH). The ALJ for Medi-Cal hearings works for the State Hearing Division of the Department of Social Services.
You typically go to the regional center for DD Waiver hearings. You go to a state or county building for Medi-Cal hearings.