Spark plug tolerances according to ISO 28741, which I suppose is the latest standard:
M18x1,5 e6/H6
M14x1,25 e6/H6
M12x1,25 e6/H6
M10x1 g6/H6
That is loose but only barely.
Spark plug taps you linked make H3 or H4 which is ok.
"General" taps for these sizes make D5-D7 - that is very loose fit.