With the visitors leading 1-0 at John Smith's Stadium in the closing seconds of the first half, Mata rounded goalkeeper Jonas Lossl before scoring, only for the goal to be ruled out for offside following a lengthy VAR review.
A number of misleading graphics showing irregular grid lines were circulated on social media and by broadcasters, furthering the confusion around the decision, before a new image seemed to show he had indeed been offside by the length of his kneecap.
Mata admits he was confused by the call but says the use of video technology is for the benefit of the game.
"I celebrated, but apparently VAR showed it was offside. I don't know. It was very tight, right?" he said to BT Sport after United's 2-0 victory.
"The important thing was that it didn't really matter because we won anyway. But it was the first time I met Mr VAR.
"You know what? I'm up for it. I think it's needed, specifically when there is a clear decision that can change the game, like a goal, offside, red card, but hopefully it will be quicker.
"But I think it's good for football to be more fair. I scored a goal, I celebrated and when I came to the dressing room they told me that even on the TV, it wasn't very clear. If the VAR is not clear, what can you do?"
Mata had set up Romelu Lukaku's opener three minutes in before the Belgium striker added a second 10 minutes into the second half to seal the win.
"[It was] satisfying for me personally but for the team, as well," he said. "We had a difficult game in the league here and we were well prepared and everyone was up for it from the start."
Asked about surpassing 20 goals, he replied: "Yeah, but I've been doing it for years now! I have to keep going. At the end of the day, I'm at Manchester United and the main goal is to win trophies.
"This win is important for us and starts us off for a good week, hopefully."