Inconsistency with implicit parameter list for traits

[acdenhartog]

class Cls(implicit x:X)
class ClsImpl extends Cls //this works

trait Tr1(implicit x:X)
class TrtImpl extends Tr1 //Compiler: Error: parameterized trait Tr1 lacks argument list

trait Tr2()(implicit x:X)
class Tr2Impl extends Tr2() //this works

trait X
implicit object AnX extends X

The relevant method is traitInits in Mixin.

So it seems there are multiple different implementations of "argument list".
Is that because Mixin phase has to occur after Erasure?