No, you've got this almost exactly backwards. It's less a problem after Tesla changed the way that they are curating their online map as it's now much better, but for many years Tesla's map was totally unreliable and almost useless as an indicator of future supercharger work. Even still, there are plenty of locations that get built without ever having first appeared as a grey "coming soon" pin on their map. And there are locations that currently have a pin but will subsequently get deleted/dropped from the map. The major problem with how they used to run their map was that when a project would fall through and the location dropped, Tesla would just leave the pin on the map if they still believed that they would put a supercharger in the area eventually. This resulted in locations having a "coming soon" pin that said the location would be built in the current year for 4 or 5 years in a row.
External confirmation of locations is way, way, way more reliable an indicator than pins on Tesla's map. And it also has the advantage that it gives an exact location for the supercharger and not just a pin that means it will happen somewhere in the city/area. Yes, relying on having independent confirmation will mean that the map on supercharge.info won't show some locations that will get built, but it means that the ones that are on the map are almost 100% reliable. This is a vast improvement on Tesla's map. And if all you want is a map that shows whatever pins Tesla's map has, then just use Tesla's map. If you want to start a thread on TMC to discuss a future location for which there isn't yet confirmation, you can do so. I personally think those threads are useless because, up until the independent confirmation is found, they are almost entirely filled with people repeatedly asking, "Has anyone heard anything about this location yet?" and others responding in the negative.