I'd first of all say, when this is on the Tarmac i'll trust it.
SSK - I'd say the route is unexpected yes, but not bizarre. When one considers SEN is marketing itself as a London airport, it's not bizarre that an airline should choose to serve it. Macedonia is hardly an overserved market from the UK.
I don't know the demographics of Antwerp too well but at a guess, there could be a sizeable Macedonian population round there and its not that far from Brussels so may not be bizarre either. There are other slightly 'strange' routes for that reason, like Tehran-Gothenburg, Porto-Dole