WSUS Update Deployemt on client machines can use internet ???

i have wsus Server  and working smoothly since 2 years. now i have   issue on some  nodes.  around 120 pcs  of one project is using an application  which is on Cloud

and we are accessing  through VPN. issue is  while pcs take windows update from wsus.it also effect our vpn link. and link chokes. As  PCs and wsus is on lan. only application access throught internet.

i stopped Wsus GPO on those 120 pcs the link  become stable.

and i observed whenever  Wsus push windows update  on pcs. pcs also start consuming internet bandwidth.

is there any connection between  Wsus update on client pc and internet ??