This is a great way to frame it with the caveat that you've done a fair bit of homework to support your assertion. And the other thing I would add is context-aware time padding. The "deadline" should be adjusted to respect the bosses schedule AND the potential impact. i.e. if it could hit production, give them more time. If it can't easily be rolled back, give them more time, etc.

But in general, if you are an adult, competent at your job, taking initiative, and have spent a bit of time thinking through the second and possibly third order effects, this is great.