I'm pretty sure you're talking about Buffalo, NY.[1] They purchased 115 semi-automatic rifles that use the same .40S&W ammunition as their pistols. That's the opposite of "high powered". And they're not fully automatic. They can in no way be construed as assault rifles.
The 450 vests they bought are resistant to rifle rounds. Their old vests could only stop pistol rounds.
I agree that many departments go overboard, but this doesn't seem like an instance of that.
1. https://buffalonews.com/2017/03/07/buffalo-police-to-get-new...