Trane Heat pump - clogged filters cause failure?

Hi All -

First of all, I appreciate any and all help offered here. I'm writing for some help in understanding a diagnosis that my local Trane service tech has provided with my heat pump and to see if I should be getting a second opinion.

I have a Trane XL 15i heat pump pared with a XV95 Furnace. The equipment is a little over 3 years old.

The situation -
The furnace was blowing cold air into the house when the heat pump was running to heat the house.
The heat pump was making a horrible buzzing noise from the area by the service door.
The fan on the heat pump was running fine
The gas furnace was running fine and pushes heat when it takes over for the heat pump
Weather has been mild for the northwest, lows in the 30s highs in the 40s and 50s since October.
We noticed the cool air about a week ago, once the noise started (or we noticed it, was able to be heard in the bedroom that shares the outside wall with the heat pump) we called the service company the next day.

Diagnosis - to the best of my ability to recite -
A plugged filter, one of the 18 X 20 X 1 air filters, was plugged / clogged / dirty. Filter was last replaced 1.5 years ago. The plugged filter caused huge pressure at the heat pump. The pressure caused such high stress it caused the reversing valve to be stuck half open when not energized and probably when energized. This damaged and ruined the reversing valve. This caused the system to pump hot gas back through the compressor. This may have damaged the compressor as well, we will not know until the reversing valve is replaced.

So my questions -
Is it probable that a plugged filter could be the sole cause this kind of failure? I can understand restricted air flow as a contributing factor, helping push an iffy part over the edge. But I’m having a hard time understand it being the sole or primary cause.

What kind of protection does the Trane heat pump unit have to help to protect itself from damage caused by excessive pressure / stuck valves or hot coolant going through the compressor? It was explained to be that there are cut offs, but that they are temporary and would have cycled on and off and on there own would not stop this kind of damage.

These are items that my me and the service tech have discussed, and he agreed that this is a unique situation. He let me know that reversing valve failures are not that common place and that he and his coworkers have agreed this is a rare situation.

I understand that if the plugged filter was the sole cause, the damage was caused by my lack of maintenance would be the culprit. I’d just like other informed opinions and experiences on the matter to help me better understand the situation.

Thanks again for any and all comments.

Dyl