I actually dont think that the shoulder nudge was overtly flirty. I think it was simply playful but not necessarily screaming anything sexual/flirtation.
Calling each other "cute" on the other hand seems much more flirty.
I think the way I am with my guy friends, shoving them deliberately is not flirty but i would never call them "cute" or "handsome" or comment on their looks because that gets flirty.
Also hand on shoulder would be casual, side hug would be casual but normal hug thats tight n longer than a few secs or holding hand between both palms like virat did would be a tad too intimate.