No, that’s coincidental, not causal. You could have no sitemap at all and Google Home would still work if the items are defined properly.
When you said this, I thought you were referring to your sitemap (since the item wasn’t correctly defined). If you’re talking about it being “grayed out” in the Google Home app, then the most likely reason I can think of is that the thermostat mode was set to “Off”, in which case you can’t change the setpoint.
