How do you use the "include" in [app-blacklist-check]?

In extensions_additional.conf, the first line of the [app-blacklist-check] context is:

include => app-blacklist-check-custom

However it appears that when I create an [app-blacklist-check-custom] context in extensions_custom.conf, it is ignored. Basically what I tried doing was copying the entire context (minus the include statement) from the [app-blacklist-check] context to my [app-blacklist-check-custom] context, making the additional tweaks I want, in order to check for certain patterns in Caller ID numbers that are indicative of a bad caller ID, such as 0 or 1 as the first digit of the area code or exchange prefix. If the number matches one of the “bad” patterns it automatically gets sent to the “blacklisted” label in the context. Except it just doesn’t work if I put it in extensions_custom.conf.

BUT, if I move the context to extensions_override_freepbx.conf, keeping the original [app-blacklist-check] context name, then it works. It’s just that it seems to me that using the “include” would be the more correct way to do it, but for some reason that just doesn’t seem to work, and I don’t understand why. Could someone please enlighten me on this?

Edit: This appears to be the same issue discussed in How to use include statement the right way? and I have posted a reply there as well.