It feels more generous because it is more generous. First, we encounter people without legs who function apparently close to normally, and cojoined twins with more than two legs. Second, and more seriously, the biological hypothesis here actually involves the brain where pretty much everyone other than a hard-core dualist agrees the actual relevant stuff is occurring. Thus, under some form of the biological hypothesis, if you took a brain and put it in a robot body that that wouldn't be conscious that would still be conscious. So I think there is some real room for being more generous to the biological hypothesis than the alternate hypotheses you propose.