Nikon's term for these was always "micro". Regarding stiff focus, they all start out that way and will loosen up, it's got two helicals, one fine thread and one very coarse. When the lube thickens a bit they can get very tight.
When I was working in the trade we got one that had sat for so long it needed a strap wrench to move the focusing ring. Cleaned it out, relubed it and all was good.