R’ Kaplan is not the only one to sanction belief in an ancient universe (or to believe that the six days of creation were not literally six days). These include, for example, Rambam, R’ Eli Munk, and R’ Dessler.
In addition, in reaction to a controversy regarding Dr. Schroeder of Aish HaTorah, R’ Sternbuch and R’ Weinberg both concluded that belief in an ancient universe was not kefirah. Indeed, Dr. Schroeder’s articles remain on Aish’s website.
R’ Weinberg (and other Aish leaders) were well acquainted with R’ Elyashiv. If the latter held that the ancient-universe view was definitely kefira, then how could they have continued allowing teaching these ideas in Aish? One is certainly not allowed to teach kefira for the sake of kiruv. It must be a valid or at least permissible shittah or the gedolim would have stopped (or denounced) Aish.