CC: Tweaked 1.109.0 to 1.109.3 removed binary chunk loading support (produced from string.dump)
However on earlier version it was working if used correctly (as stated in #1604 )
Example:

local file = fs.open("my_bytecode", "wb")
file.write(string.dump(function() for i=1, 10 do print("Hello",i) end end))
file.close()
-------
local file = fs.open("my_bytecode", "rb")
local fun = loadstring(fs.readAll())
file.close()
fun()

now it is broken
Removing a good feature for at least some security from outer or unattended edits/reading is pointless, unless good alternative is present, like do not allow reading another computer's file using disk drive by default
To avoid jvm errors, a lua check is needed, for example string extracted from file opened in binary mode get special meta-value that is checked before loading the byte code. If it is not present, throw an error like "Binary chunk is corrupter (Be sure to use *b file mode)"

As I mentioned in #1604, Lua's bytecode is a bit of an implementation detail, and should not be relied on, as it changes between Lua versions. Indeed, in CC:T 1.109 we updated our Lua VM to Lua 5.2, which made several breaking changes to the bytecode format.

#1615 goes into this in more detail, but as part of that upgrade, I made the choice to just remove bytecode loading entirely, at least for now. I definitely appreciate it makes some programs a bit of a pain, but I don't think it's worth the implementation and maintenance complexity.

As far as your specific use-case, I think it's worth mentioning that Lua bytecode is trivial to decompile, and thus doesn't really add any extra "security" or protection over just minifying your code.