Step to reproduce,

1. Load the behavior pack (castle) into a flat world.
2. execute the top level command /Function castle

Execute a function (.mcfunction file) with more then 10k commands. I have done this with all commands in a single file and with a function file that calls child functions.

Result:

I get the message feedback,  Successfully executed 10000 function entries.  

Expected Result:

I expect that the system would execute the number of functions set by the maxCommandChainLength gamerule value. the default being 65535