I believe it’s that Bloom’s study implies that 1-on-1 pacing and teaching produces the best learning results, but that Bloom thought it was infeasible to scale to everyone: it’s “too costly for most societies to bear on a large scale”
There are a few potential options that appear in or occur as one reads the literature (the linked Wikipedia article lists several references, beyond Bloom's own work). That includes inflection points in the effect, that is, some advantage occurs with lower degrees of specificity, particularly with instruction at a 1:10 -- 1:15 instructor/student ratio or so. Another option would be to randomly apportion tutors to the general population, or to assign tutors either to particularly talented students (regardless of family wealth/income), or to specific underprivileged populations (to reduce systemic and historic educational gulfs), or simply at random (which avoids numerous social, political, personal, and/or academic faddish biases).