I’m not sure you really understood the point here. You contacted Athom about 3rd party / “official” developed app, so they correctly redirected you to the app support itself. Then you got from Community answer, that you shall use GitHUB for this app, which you did but the developer denied this suggestion, because you did not share all the details, except of generic answer from Athom suggesting chatty device - Slow Z wave response - Leviton Polling Interval Default · Issue #12 · koktail-nl/com.leviton.issues · GitHub
Your issue seems to however be more complex one and neither of the way could be correct in this case. I suggest you to share ZWAVE view Homey Developer Tools from in the Homey Z-wave communication very slow - #11 by California_Dreamin and hope that someone from the community will help. If it will be confirmed that chatty are actually Leviton itself, then I would suggest to open new Github issue and address it to the developer.
