It's there via omission. Others have said in these threads that the concept of an HVAC company or others investing in a particular manufacturer, does cost them money, and that can change over time. It's not unique to Tesla, but the writing, by way of omitting this.
"That is the bind Tesla’s certified installers are in: dependent on a brand that just walked away from a product line they built a business around, while still needing to sell its remaining hardware."
there is _nothing_ unique about that situation. That could happen with any company.
It's the cost of doing business. training your workforce, etc. Clearly these companies are happy to sell other Tesla products to the point where they don't want to jeopardize those relationships.