Not necessarily
For example firewall with around 40 rules - adds around 100kbps in spikes.
Interfaces window with 10 interfaces - 80kbps, almost constantly.
IPsec Installed SAs with 10 items - 20kbps.
So opening a bunch of windows can easily create a constant bandwidth of 200-250kbps.
As was already mentioned by @nescafe2002 - if it becomes a problem, one can always use ssh.
It should not be that way.
That is winbox connections to 4 different routers:
Lower 3 have no open windows, only cpu/time/date/etc in the dashboard.
Upper one has an open IP → Firewall → Connections from where I took a screenshot.
So it never rises over 5kbps/10kbps (To winbox/From winbox) for the ones without windows open.
So check again that it is a single winbox connection and not something else on the router.