I don’t think that /etc/sysctl.d has been deprecated. Can you look through the other files listed there and see which one(s) are overriding /etc/sysctl.d/10-huge-pages.conf? Maybe one of those 50-priority files?
The better solution will probably be to change the priority of the huge-pages setting to win. But I am not running either of those versions right now on my systems.
Also check whether tuned is overriding the setting.