Tires do not really fit despite the same size designation!

Hello in the round, is that actually still normal, what I am experiencing? Sometimes I really doubt myself. Vehicle: Citroen Jumper II Tyre size: 215/75 R16 C Previous tyre: Continental Vanco Winter2 (as 113/111 R) Current tyre: Goodyear Cargo Ultra Grip (as 116/114 Q), slightly rougher than the previous one. Happy and satisfied that I could spontaneously (can you “mount” now?) pull the tires on it just before worktime – the sticker due to lower speed “The tires are too big, with a strong steering impact they grind somewhere.” (With the old tires never had problems, the size is out of the vehicle’s license, were just at the wear limit.) I: “Can’t be, there has been the same size as before, just another manufacturer.” : “Yes, that can happen however, that despite the same size designation the manufacturers interpret these (I’ll shorten the time) differently. 215/75 R16 does not have to be equal to 215/75 R16.” I: “Well, great, and now?” Conclusion: The cart stands now and is not driven. Can you really not rely on it nowadays when the size is on the flank? What does that stand for, if it is not true? Should one now measure yourself? Why pi*** then the tuv actually still stands if deviations are above x% (registration / speedometer adjustment due to different tyre size), if not even the same tyre designations provide an identical result? I can no longer come with …