It is for now. There's a serious bug in the compiler for tchelp.exe that the developers have not yet been able to fix. There are also several bugs in the Microsoft .chm help, but I was able to kludge around most of them for v21.
In the long term, Microsoft has dropped .chm support so we will eventually have to move to something else (tchelp.exe, web help, or something new).
Hoping that offline (non-web) help will continue to be an option in future versions of TCMD/TCC, whatever form it may be in, because it isn't always possible for me to have my laptop always connected to the internet (e.g. while on the bus/train/using public transit, or in other public places where there is no Wi-Fi or wired network connection available). That's why I hate this trend of Microsoft trying to get everybody to exclusively use web-based help. Plus, it's slower when my web browser has to open and load a webpage every time I want to get help on some particular topic. I'm glad that web help is an option, but local (offline) help should always still be an option, for all programs.