I'm guessing this is the result of Google using their own hardware.
Because, if they're using chips from other manufacturers, those chip manufacturers may not provide firmware updates or driver updates for extended periods
Also, it was very much needed. I hope they extend the support period for pixel 7 too
This is similar to Fairphone's situation. For the Fairphone 5 they just use an IoT chip with long term support from Qualcomm enabling them to give at least 5 years of feature updates and 8 years of security patches.