Your description of fit check isn't clear. If you're talking about cultural fit, then be prepared to be disappointed because there are many companies having this as a round where there is going to be a clear mismatch between what the HR "wants" the culture to be versus what the actual culture is going to be working under your boss whoever that is.
Sometimes it's very easy to clear the culture fit round by the HR but the line manager whom you're interviewing is going to behave like an absolute jerk either during the process itself (lucky if this happens!) or once you join the organisation. This will eventually make you question the entire culture fit process.
Consider it luck or coincidence if you find both the cultural fit the organisation aspires to have and your boss showcasing the same. Easy to find this in smaller organisations but larger the size lesser are the chances.
The other obvious fit is the budget fit. They just call to hear out your current salary and never get back if it's outside their budget.