Why does iPhone h.265 video have to be transcoded?

Can someone explain why every time I shoot h.265 and airdrop it to my iMac, it goes through a long transcode process? Didn't the latest FCP X upgrade to h.265? Is it transcoding for other apps that haven't been updated yet? And is it using the h.264 transcode or does FCP X natively use h.265 yet? Thanks.