Traditionally X factor goes for those contestant s who are a bit of a blank canvas style wise, easier if they are young as potentially more pliable. I get the feeling that Seann, Alien and First Impact haven't really liked to change what they have established as a style for themselves, either in their fashion style or their musical direction. This played out with a First impact and Alien not liking the song choice and Seann being unhappy with his outfit.
Potentially if they don't toe the line, could they be de ramped, or in Aliens case, made to look awful in their sing off. They did this before with Janet Devlin as she started speaking her mind.

Why on earth are they dressing up Fourth Impact like Minnie Mouse?

I remember Lillie McCloud being eliminated right after she stood up against Simon, when he critiqued the way she performed. (X Factor USA)

Alien made to look awful? They were awful of their own doing. Tragic.

They're dressing them like they dressed Fifth Harmony when they were on X Factor USA

Doesn't suit them, I think they look better dressing themselves

It was the first time I had seen Seann in trousers and I think that was a deliberate choice by producers to make him more 'acceptable' to (their perception of) the GBP. I think he looks great in a dress and heels and would prefer it if he could collaborate with a sylist and invest in some designer dresses, to develop his own personal style

To be fair they have never had any idea of how to dress the contestants. Poor Misha B was made to look ridiculous with some of the clothes they had her in.

I seem to remember one week she looked like a Quality Street