Why does renaming ListConcatenator with colon cause the workspace to fail?

I am using several ListConcatenator transformers in my workspace. I want to give them unique names, however, when I rename them and run the workbench, it fails and gives me an error. When renaming my transformers, I normally use an abbreviation for the transformer name followed by a colon ":" then some unique name. For some reason the ListConcatenator doesn't work when a colon ":" is in the transformer name.

Example: I rename the ListConcatenator transformer to "LC: RunwayNameList" and it throws this error:

2020-03-02 08:32:52| 2.2| 0.0|ERROR |@Tcl2 -- failed to evaluate expression `set LC:_RunwayNameList__separator [FME_DecodeText {<comma>}]; regsub -all "{}" [FME_DecodeText {_listAll<opencurly><closecurly>.RUNWAYNAME}] [FME_DecodeText {<opencurly><backslash>d+<closecurly>}] LC:_RunwayNameList__listPattern; set LC:_RunwayNameList__listPattern ^$LC:_RunwayNameList__listPattern$;' -- can't read "LC": no such variable

It seems to be isolated to the colon ":" that I am using. If rename it to "LC_RunwayNameList" it works fine. I am able to use the colon ":" in other custom transformer names. Is this a bug or normal behavior with a colon ":" include the ListConcatenator transformer name?

Thanks in advance!

Version: 2019.1.2.0 (Build 19630) 64-Bit