In some ways, that is a correct description. But, let me make some clarifications.
First, if you did not include the optional "Purchase Likelihood" section in your ACBC study, then the None parameter that is estimated is not really a true "None" utility as from CBC. Rather, the None parameter is derived from the Screener section, and is the utility associated with the alternative labeled "not a possibility". Recall that in the Screener section, the respondent is presented a series of product concepts and is asked if each of those is a possibility or not. That section of the design matrix is coded as a series of binary choices (the product alternative vs. the "not a possibility" alternative). The None utility is the utility of the "not a possibility" alternative. As you can see, this really isn't the same as the None alternative from a standard CBC questionnaire.
When the respondent indicates a "must have" or an "unacceptable" rule in the Screeners section, then we look to any of the near-neighbor concepts that have not yet been evaluated by the respondent. If any of those concepts would be rejected per the "must have" or "unacceptable" rule that the respondent has confirmed, then we make it look like the respondent indeed evaluated those additional concepts and marked them as "not a possibility". Those inferred choices are added to the design matrix as if the respondent had explicitly seen them and answered "not a possibility". Therefore, this information is indeed represented in the design matrix.
