The spy pics you see are often "meant" to be seen, and yes, this has been going on for decades (including the "Highland" leak IMO). How many Model Y spy pics did you see before debut? Tesla has been producing Model 3 Performances for about a month in China, did Tesla start taking orders for them last month for it? Maybe this is Tesla finally growing up, and a new way of doing things. Lets hope, I do believe the long CT gestation taught Elon a lesson. Have the product ready, or near ready before debuting.
If this is a new car on the Y platform, the engineering started last year. In the car business many projects are studied but never green-lighted. The idea of building new cars off the Y platform is not new. We were shocked that there was a Gen 3 platform, until then we assumed new products would be a variation of the Y platform. Years ago, there was a strong rumor of the Model S shifting to the 3/Y platform. Never happened but I bet Franz has a file of designs and engineering data if needed.
Too many people are taking the events mentioned in the Biography of Elon book literally. Was the writer at the "other" meeting where this decision was made? This decision could have been made right in front of the writer but was engineering ignorant to recognize what Elon, Lars, and Franz were saying.