I’ve always considered the first 4x0% post as the start of development, and why wouldn’t I? What evidence is there that he’s doing any development, scene creation or otherwise, between release date and first progress report?
I think it’s more than reasonable to figure Renders per day based on first progress report and CS & rendering @ 100%.
I would agree that your method is more accurate to figure out renders per day if L&P's progress bars are also accurate. You use 4x 0% as an indicator that the developement of the new update has started, but you cannot be 100% sure that it is like that. You cannot say for sure when he actually starts developing, unless you trust the progress posts from L&P.
But everyone can check when he releases his updates and how many new renders are included. That are the only facts you can proof and trust.
The drawback in your method is that you are not considering L&P a human. This method treats him like a machine who immediately has to get to work after the update is released with no rest, no break and no personal life, no falling Ill and no days off, no time towards planning the next scene and so on. Just a man who must make this game 365 days a year.
So there are drawbacks to that too.
I'm not sure but didn't L&P himself said that he works 11 hour a day, every day? When some people talked about how he would take a 2 week break after every update, he denied it and said that in this 2 weeks he would answer mails and other stuff beside rendering.
L&P posts for every new update the approximate release date with the render count. So he uses the number of renders as an indicator on how big/long a update is. And I use this information to track his developement speed over the time by calculating the average renders per day for every update. It is just an simple illustration.
Most likely he has done more renders that didn't end in the game, and some renders can take more time as others. Also he doesn't just only do renders, there is also scripting, programming etc. And as you said he probably doesn't work 365 days a year, most of us would agree on this.
But nobody but himself can tell how much he works, how many renders he does and so on. The only information you can check is the release dates and render count for the updates.
People can check with the data I collected, if the developement speed got slower or faster in a certain timespan (no matter what reasons caused it). It's a useful information for people who consider to support him financially or are already doing it. They should at least know what they are getting into.