5.4l triton 3v cam

Hi. Have a question on the cam of a 5.4l triton in a
2007 f150. I am having engine problems so I done
a compression test and was attempting a leak
down test. I got no compression on #8 cylinder. I
took off the valve cover to check everything. I
started to hand crank my engine to get to TDC and
while cranking the cam would jump an 8th of a
turn. The timing chain was fine. It was the cam
phaser turning internally. My question is can I trust
my tests if this is happening and is it normal. I
have got different answers from different
mechanic. One said it was normal because without
the engine running there is no oil pressure to fill
the phaser and therefore letting it move. That
sounds right but doesn't seem right. Any help
would be appreciated.