[Diamond]

No, the reason why we exclude ID if nothing is known about the supposed designer is the fact that it is not falsifiable.

I would say that falsifiablity in the sense of positive verification by direct observation cannot be had in any historical inquiry. Requiring that the postulated entities necessary to origins theories have to be directly observable if they are to be considered testable and falsifiable and therefore scientific would rule out out common descent as well as ID. There are myriad Darwinian hypothetical postulations of past, unobserved and unobservable 'events' that purport to account for present biological facts and data that cannot be directly tested either.

Cordially,

[BMCDA]

But we can directly observe the nested hierarchy which is supported by several independent lines of evidence (cf. Ichneumon's posts).
If evolution were false this pattern shouldn't be there but both scenarios are compatible with some unspecified designer.