Right, 100 trucks delivering 100 single items to 100 homes, or 100 consumers each making 1 trip to buy 100 things. It really depends on the details too much to simplify it so far.
With there typically being a free shipping minimum (or a relatively fixed shipping cost for daily goods), it seems like the benefits of the 1 truck model are likely even greater as customers are explicitly encouraged to group purchases together.
For the aforementioned 100 homes, if the 100-items-in-1-truck are needed multiple times per week, then the 100-items-in-100-cars are likely also needed multiple times per week, so the extra CO2 etc would be even worse.