The reasoning appears to be that if the BHs are clumped, then the number of microlensing events will be lowered, as opposed to if the BHs are evenly dispersed.

The reasoning appears to be that if the BHs are clumped, then the number of microlensing events will be lowered, as opposed to if the BHs are evenly dispersed. In other words, the number of concentrated masses intercepting rays of light from distant background sources would be given by the number of BH clusters as opposed to the number of BHs. The objects we're looking for are large masses in the space between us and the distant light source. Typically the light source would be in the LMC or in our own galactic center, and the BHs would be, for example, in our own galactic halo. We wouldn't expect to be finding BHs in a distant galaxy by microlensing. I'm describing (or trying to describe!) what seems to be the astrophysics consensus. Sean Carroll is a Caltech astrophysicist who was interviewing another astrophysicist, and my quote from the article gives the explanation from a third. Am I getting this wrong?