Because, as Redwood and others pointed out, and I demonstrated in
post 109, you're being sloppy. The brick does not decelerate, it continues to accelerate. It's also not correct to say that the velocity changes at the same "instant" (for purposes of discussion) the acceleration changes; that would require an infinite acceleration.
I'm not sure why I got involved in discussing bricks through tissues anyway. The issue I've been trying to help you with, most recently in
post 58, is much more important for you; it's the failure to
validate your understanding of the problem, and the closed loop you have locked yourself into in terms of evaluating what everyone else has to say, which requires you to reject everything that disagrees with your conclusions.
Logically speaking, you've painted yourself into a corner with Super Glue[tm]; dealing with that, so that you have the ability to learn and consider the possibility that you may be wrong, is way more important than whether you understand the difference between a change in velocity and a time rate of change.