You have to remember that Joachim was only 18 and is still the youngest scorer in the Division One/Championship PO Finals. An absolute cracking talent, so it's very relative.
He only makes a ''lowly'' eighth place on the all time youngest goal scorers at Wembley Stadium though {old and new}. Interesting that the only team internationally to make this list is Brazil - both in friendlies. Norman Whiteside is the most consistent, and Crewe match Man Utd in adding a player {or the same player} to the list in successive seasons. The more incredible stat is that all in the top ten are all under 19. Joachim is still one of the youngest to score in one the most high profile Wembley matches, with only Whiteside and Sisson playing in a match of similar pressure {we could argue the Div One PO Final is even more pressure, due to the high stakes nature offered}.The only surprise to me, is that someone like Wayne Rooney isn't on that list - unless he was or is it possible he misses out due to the ''Millenium Stadium'' era?

Anyway, here's the list
Endrick – 17y, 246d – Brazil vs England (Friendly, 2024)
Norman Whiteside – 17y, 323d – Man Utd vs Liverpool (League Cup final, 1983)
Norman Whiteside – 18y, 19d – Man Utd vs Brighton (FA Cup final replay, 1983)
Nick Powell – 18y, 65d – Crewe vs Cheltenham (Fourth-tier play-off final, 2012)
Damian Spencer – 18y, 210d – Bristol City vs Stoke (EFL Trophy final, 2000)
John Sisson – 18y, 215d – West Ham vs Preston (FA Cup final, 1964)
Max Clayton – 18y, 242d – Crewe vs Southend (EFL Trophy final, 2013)
Julian Joachim – 18y, 254d – Leicester vs Swindon (Second-tier play-off final, 1993)
Ronaldo – 18y, 262d – Brazil vs England (Friendly, 1995)
Peter Barnes – 18y, 264d – Man City vs Newcastle (League Cup final, 1976)