It is absolutely the case that the Roshei Yeshivos since Rav Ahron supported a no secular studies arrangement in Mesivtas under ideal circumstances. The various Roshei Yeshivos may have had different opinions of what ideal circumstances were that allowed a Mesivta to forgo a secular curriculum. Some felt that many parents wouldn’t send their children to a Mesivta with no English so they permitted secular subjects to prevent the bochorim from being sent to worse schools. Others may have felt other criteria needed to be considered whether to allow or forbid secular studies.
