No it’s almost certainly true. If you’d like some estimates you should read up on scott Alexander’s pre and post substack revenues. For writers with large followings substack is like a 10-100x monetization boost over other options.

Source: my publishing company published three books of Scotts essays during COVID, hit number one two and four on the essay category on Amazon, and generated less than one fiftieth of Scott’s first year of substack revenues based on his public comments.