Perceptive bias should only have worked if I expected and wanted them to sound good when I wanted and expected the opposite.
That is not how perceptive bias works - it is an unconscious and automatic process. It can be influenced by your conscious expectations, but it does not need to be. It can also result from unconscious filtering built from everything you have heard, seen, read etc regarding the topic. Or from completely unrelated stuff in your senses pre-filtering. Even when you are aware it is happening, and why - it is not possible to stop it.
But here is a thought experiment.
(Note - audibly perfect here means deviations between the master and what is produced at the output of the DAC are too small for our human hearing to detect)
PCM encoding delivers an audibly perfect representation of the recording.
MQA encoding delivers an audibly perfect representation of the recording.
If the master is the same (And assuming the DAC reproduces both encodings at the same level): Two audibly perfect representations of the same master (at least as far as the sound waves reaching your ears are concerned) must sound the same.
So that would leave the following possible explanations for your perception.
1 - Different master
2 - Different level (even small level differences not heard as a volume change can alter the perceived tonality of the sound)
3 - Perceptive bias.
The only way you can know for sure (assuming the masters are the same) would be to do a well controlled blind test. These are sufficiently difficult to get right that the benefit of doing them (knowing why you are hearing what you are hearing) rarely makes it worth while. Though lots of people here have done it anyway, myself included, - and found themselves amazed that differences they thought were obvious - disappear once they are listening without knowing which source of the sound is which.
