Not all biological POD belong to ASB: Jared's 'Lands of Red and Gold' lay on biological POD, the fortuitous hybridization of two plant species.
Besides, a taboo on OTL biology would logically imply that it is itself determined by an ASB.
The point is Alternate History (as opposed to historical fiction / fantasy, how possibly enjoyable and stimulating it may be) is based, referenced on OTL history. Then, some time (time varying among other factors with the 'importance' of the divergence) after *any* POD ATL has diverged so much from OTL that almost no reference is possible, one can write (almost) anything and the exact opposite. And here we require a POD a billion years in the past.
About 'cellular', in French cellulaire tends to be restricted to Eucaryotes, so the question would be what if Eucaryotes had remained marginal: can Procaryotes (bacteria) evolve to complex organisms, differentiate tissues and organs more than slime molds (Myxobacteria) do? And the question implies an earlier POD, explaining why the eucaryotic cell did not appear or was out-competed...