This is clearly regional. I'm in the US where we don't measure in MM. Different parts of the world will have different standard sizes. you might be able to import a US standard door if you wanted to use 88.9mm widths for some reason (there is more than enough tolerance to round that to 90mm), but it would be extra effort on your part. The hard part about importing it often codes are designed to limit this, so even if the US door is better it might not meet some standard that shouldn't even required. (this goes both ways, US standards often require things just to limit imports as well)