The Site Diagnostic now applies body length thresholds that fit English pages. Body length is counted in characters for Korean pages and in words for English pages, but the per-page-type thresholds did not account for that difference — so English pages scored lower than they should have.
Korean pages keep their existing scores and grades. English pages may gain points on the body length item, raising total score and grade, and because the standard changed, comparisons against past results restart from your first diagnostic under the new standard.