Why are howitzer garrisons so broken?

I arrive at the firing possition with R-17, fire one coontinous salvo - howitzers shot back at me within 2 secons - fair enough

Then I undeploy and move to other location, like 30ms away, and somehow howitzers again shot directly at me... why? Like, what's the lore explenation for that? Are howitzer garrisons alting, or sth? How can you know location of a mlrs, which after firing its load have already relocated, without having any visual on it?

EDIT:

To clarify I am not asking how it is done on technical side, but how is tihs suppose to make sense, given the game setting