Optional function tags sometimes don't run even when the tag exists

The bug

When function tags are in a particular configuration, certain functions don't run when you would expect them to. I attached a data pack with the least amount of files needed to reproduce. This configuration has 2 function tags and 2 functions. When loaded it is expected to print two messages in chat, however the observed behavior is that only b:load runs.

#minecraft:load
  -> #c:a
       -> a:load "say load A"
  -> b:load "say load B"

It depends on the names of the tags and functions whether or not the bug will happen!
For example, renaming #c:a to either #c:load, #minecraft:a or #a:load will not cause this bug!

Files

{
    "values": [
        {"id": "#c:a", "required": false},
        "b:load"
    ]
}

{
    "values": [
        "a:load"
    ]
}

say load A

say load B

How to reproduce

1. Download the attached data pack mc-201840.zip and install it in a world
2. Run /reload
3. Observe that only "load B" is printed
4. Do one of the following actions
   • Replace "required": false with "required": true
   • Rename #c:a to #c:load (and update reference in #minecraft:load
5. Observe that both "load A" and "load B" are printed