Need advice 360 timing chain cam/crank slightly off

Purchased a 360 from Mabco to put into my A66 340 Challenger short term while I pull the 340 for a rebuild.
I bought a hp version with flat top pistons and installed hp cam sited as a 272 cam
Cam specs; 272-272 duration 454 lift 110 lobe separation 52 degrees overlap, 216 216 duration @ .50
Power range 1500-5200 Considered the largest "stock" cam for this engine
In going over the engine for parts install; the timing marks are slightly off.
I call the manufacturer and he stated to leave the chain as is.

Pistons are flat top 30 over, no valve notches, piston to deck measurement is not a stock (deep in the hole) 360 with the higher compression pistons it measures out at about .087 below deck with number 1 piston at TDC.

I am no expert, and I have installed cams years back always aligning timing marks; is there a reason for the manufacturer to alter the timing in this manner with this hp cam and flat top piston?
Pic of timing chain sprockets and Number 1 piston at TDC
Any thoughts appreciated.

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