Is it now please elaborate why this is wrong...
Happy to. Here we go:
Your tall & have big feet so the SL and the Heritage don't even bother with unless you enjoy toe drag which you don't...
All rubbish. Specifically:
1. Height matters very little for board selection or sizing.
2. His feet are not that big - size 12 are just borderline for wide boards. Depending on stance width, stance angles, board sidecut, bulkiness of boots, etc. a size 12 might actually still work with a regular width board.
3. He was not asking about the regular width Heritage, but the (wide) Heritage X.
I suggest at least a minimum of a 26cm board waist for a size 12 boot...
Waist width is irrelevant, what matter is width at the inserts/binding positions.
Your also over 6ft tall I wouldn't go any smaller than a 158cm but you'll outgrow it very quickly and suggest going with at least a 161cm...
Rubbish. As mentioned, height has very little to do with proper board sizing. At 6' he could be riding anything from 150 to 165, depending on weight, conditions, riding style, etc.
The Heritage is more suited to a heavier rider than you are which would make it more work to control for you at 165lbs...
Utter garbage. So Heritage is for people weighing more than 165lbs!? How much would one have to way for a Raptor then???
IMHO I think the Legacy 161 would be your best choice for an all mountain board ...
Keep in mind 3cm is a little over an inch in length not a huge difference but even though you are skinny feller you are tall and have big ass feet which make your biggest issue finding a board wide enough to accommodate a size 12 boot...
Wrong. The opposite is true: Since he is a lightweight guy on a wide board, he should definitely try go shorter if possible - that is why I recommended considering the 155, the 158 will be plenty.
Heres a quote I found to support what Im saying as a general rule of thumb: "If you are going to be riding the whole mountain, you will want to go for a board with a waist width of at least, say, 258mm. This is generally where the mid-wide category begins. Riders with boot sizes 11 and 12 may be able to get away with a waist as small as 258, but will probably find something around 260ish to be most comfortable. Riders with size sizes 13 and above should stick with a full-wide waist width at least 265mm."
Also keep in mind all boots are different where a size 12 in one brand could be as big as a size 14 in another or like the new Burtons where a size 12 has the foot print of a typical size 11...
You added this after my response, but it's ok - in fact, I have pretty much addressed all those points already.
Two key points:
1. Height matters little for board selection and sizing.
2. Foot size needs to be compared with width at the inserts/binding positions, not waist width.
Both of these this things have been highlighted many times in this forum. You are perpetrating old/outdated approaches that were wrong to begin with.