This is what our friend Dale Johnson said:
"It's a controversial decision, and goes right to the heart of what is a "deliberate play" by a defender. There is no doubt Salah is in an offside position, but if the officials judge Toti's actions to be a "deliberate play", Salah cannot be penalised or offside. In short, a "deliberate play" only applies when a defender has control over where the ball goes. There are many factors which are taken into account, and an attempted header is judged more in favour of the defender than a kick. This is because there is, generally, less control in heading a ball. Mohamed Salah is offside when the ball is played by Cody Gakpo. If a defender has to stretch or jump to head the ball, this is an extra layer for determining that it's not a "deliberate play". Dean decided not to intervene in the on-field decision to allow the goal. However. we are likely to see similar instances where a goal is disallowed. It's a hugely subjective area of offside, and Wolves can consider themselves very unfortunate to have conceded this goal too."
This is as close as he will ever get to saying Dean made a mistake.