Sub-categories do not 'auto-appear' under links tab?

Setting up categories in 2.3.0 and problem occurs when setting SOME sub-categories. (i.e.) Main category HATS and then sub-category HATS > Mens. For some reason under the product LINKS tab to establish category links SOME 'sub category' links do not 'auto-appear'? (i.e. I get HATS but nothing appears as HATS > Mens). The sub-category is there in the 'CATEGORIES' listing ( but images only appear when 'show all hats' is selected, no sub-category appears)?

UPDATE: Found that I have to type in HATS > Men's (with apostrophe for it to auto-appear under the LINKS tab for the product)? HATS > Mens (with no apostrophe) will not appear? BUT I do not have the same issue with HATS > Womens. Requires no apostrophe to appear?