Why would he copy my tone of voice/ the way I speak subconsciously?

He works at the local store...I wen there with my mum, she spoke to him first and he was very polite as usual and spoke in his regular way but as soon as I spoke he changed the way he spoke to mirror/ copy me and even had the same accent/ intonation!

What does this mean and why would he do this?

Why would he copy my tone of voice/ the way I speak subconsciously?
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