I may have missed it but I don’t think intervals will automatically update your FTP (or W’) in /settings as used for this calculation, or at least mine doesn’t get automatically updated!
Another consideration though if your FTP is set “correctly” is that it might still be too low and you need to do a consistently paced FTP test to determine what your actual FTP is right now - considering this ride gave you a “new” FTP even though it was very surgy.