My last post contained some misinformation so let me correct and sort of answer myself. After inspecting the unit more and doing a little research I found that my wiring is actually exactly like this unit: Understanding and Wiring Heat Pump Thermostats with AUX & Em. Heat! Terminals, Colors, Functions! - YouTube
Since W is actually emergency heat not primary heat then I believe only Y needs to be powered for heat. So the wiring for that would look like this:
This wiring configuration seems to be common in my area, specifically hvacs with 1-stage Lennox heat pumps.
I haven’t gotten my HestiaPi unit in yet but I will report back with my findings in case it helps anyone else out reading this in the future.