You guys will confuse people. OP has 2.5T and Mazda says it’s 5.1 quarts for oil change quantity. But for 2.5L it’s 4.8 quarts for oil change quantity. Many 2.5L owners put in 5 quarts for convenience but it still below Full / Max mark by least ⅛ quart、 or ⅛ between Max / Full and Min / Add marks. Now you guys say using only 5 quarts for 2.5T which is 0.1 quart less than Mazda’s spec? Other 2.5T owners have been using 5.5 quarts for oil change which should bring up the oil level to the Max / Full mark.
One can measure the oil level hot or cold, whichever way you prefer. It’s been proven they won’t make too much difference.
What is there to be confused about? Is 5.1 quarts not "about 5 quarts" as I stated, and as you highlighted in bold? The only confusion I'm aware of is your mention of the 2.5 NA, since both the OP and Ladd have 2.5T-equipped CX-5s, and the discussion has been regarding only that engine (until you brought up the 2.5 NA in this post).
As I have mentioned in my responses to you in particular, about filling the oil - it's personal preference, and the exact amount required depends on a lot of other factors (drain time, prefilling the oil filter, oil level preference, etc.). To account for all of those variances, an approximation of about 5 quarts
is logical, with a suggestion to keep an extra quart of oil on hand to account for oil level preference.