Progressive formats still require the device and network to allocate the bandwidth appropriately, so you'd want required traffic reaching the device first, and then images. The problem is that in most cases everything is just thrown more or less at once towards the device and then latency and packet loss goes through the roof and nothing loads.
But wasn't progressive JPEG and AVIF pretty much designed to alleviate this problem though? Webp does not seem to support progressive loading however.