It's really a blessing in disguise. The lecturer in charge of assigning students to supervisors already did a lot of work assigning students to supervisors. Getting you assigned to a supervisor was an extra task for him. And it came up when he thought he was done with assigning of students to supervisors. So, naturally, you'd make his additional task a lot easier if you chose your preferred lecturer.
I can relate to what it feels like to be assigned to a mean supervisor because I experienced it too. So, I'll say "congratulations" to you.
Thank you so much..