The Tottenham Hotspur striker was hauled to the ground in the Tunisia box on several occasions during the Group G encounter before eventually grabbing the winning goal in injury time.
"We recovered well from a really harsh decision and kept our composure," England boss Southgate told BBC Sport following the 2-1 win over the Carthage Eagles.
"In the second half we looked for opportunities rather than throw balls into the box. Our attacking set-plays were a threat all night - we got just reward for that.
"I think if it's a penalty at one end it has to be a penalty at the other. If penalties are given for that then it's going to be an interesting tournament - there were similar offences at the other end."
VAR is in use at the World Cup for the first time this year, but the system has already come under criticism several times.