Not a logical fallacy at all. Although there may be a phrase which might describe the possibility of it being one.

Yet another unintended consequence of Brexit has been raised (again) today.
"The Chartered Institute of Personnel and Development (CIPD) said the number of applicants per vacancy had fallen since last summer across all levels of skilled jobs, and said shortages were forcing many companies to raise wages."

If Brexit is causing a rise in wages, how do you square that with the insistence that membership of the EU, and EU immigration was not supressing wages?

The only logic required is the logic of the marketplace, of supply and demand.
Looking at available labour being the commodity supplied, if there is a shortage of available labour, and demand is constant, the cost of the labour will rise.
If there is a glut of available labour, and demand is constant, the cost of labour will fall (Although it can be propped up by 'minimum wage' rules).