I'm a fitbit user. When a technical support of fitbit requested me to 'clear cache of fitbit app' on my iPhone11 Pro,

I asked how to do it? Then the technical support send me the instruction on this page, which is to clear cache of Safari. I follow that instruction, but that didn't resolve the issue of fitbit app.

My question here is, does 'clearing cache of Safari' actually clear all the cache of any app running on iPhone???