Let's compare some individual elements. Here are two of the same words from both inscriptions. To me they look like they were written by completely different hands.
Here is the same diagram, but I have circled the areas that have the most discrepancies in corresponding colors.
NEON GREEN: 'Z' on calendar does not have a stroke through it.
RED: Bottom of 'Z' loops on calendar, resembles cursive '2'. I didn't circle but the top of the 'Z' also does not match at all.
BLUE: 'P' on questionable inscription is two strokes, real one uses one stroke.
ORANGE: 'D's on questionable inscription is two strokes, real ones use one stroke. The 'D's on the real one also loop, while the questionable ones do not.
DARK GREEN: 'K's are just completely different I don't even know where to begin.
PINK: This is the part I found most interesting. One of the features that the handwriting expert pointed out on the questionable autographs is that the signer sometimes put a little tail on the end of their "A"s, while the real Luka signatures tend to not have any tail at all.
And low and behold, not one but
two of the 'A's on the questionable inscription feature the tail on the 'A'...
I do not believe Luka ever stepped foot anywhere near that calendar.