Just took JKO - Grenades vs Booolets?

This question is strongly inspired by my logging onto Reddit and seeing this thread.

https://old.reddit.com/r/AskReddit/comments/1pg6ijc/what_is_a_survival_myth_that_people_believe/

CONTEXT: Somewhere within the last 6 months I took a training as a civilian from JKO. It made a VERY big deal that you should get on the floor for bullet shrapnel but you shouldn't for grenades. The fact they even differentiated the types of attack was weird to me. I was tested on this TWICE. I want to re-iterate that I'm a civilian and I've never seen, touched, nor heard a grenade. (I would throw one if you let me but I don't think that's possible as a civilian). The only boolets I've been around are from my own civilian arms collection. This was 100% an online training and apparently I was supposed to learn how to differentiate people infiltrating the building with guns versus grenade launchers? This seems like a whole bunch of "not my job."

PRACTICAL QUESTION(s):

1.) Do Grenade and bullet shrapnel vary that much?

2.) Enough I need to be concerned

3.) How (without ever being near it) would I know a grenade versus a bullet report anyway?

FOLLOW ON: I work in a job where-in if I am actively being fired upon innumerable things have gone wrong. My fate has been sealed well prior to whatever impacts me. When the situation gets to me I'm just along for the fucking ride at that point. I can throw a punch and to quote a certain great theoretical president "I will not go quietly into the night" but yeah... there's no real options for me.

I did the training because my employer paid me to do it. Otherwise I wouldn't and I certainly billed accordingly.