moving maps between difficulties is MUCH easier said than done due to a number of factors (rotation, database updates, completion transferring) which makes the whole process not worth the huge investment to do even ONE map.
your problem is indeed a disparity in difficulty and the examples given DO show a highlighted flaw in specifically the hard difficulty, trying to bridge the gap between medium and expert is a very LARGE gap so of course some extremes in both sides will feel like mediums or experts (theres also way better examples than 2 maps that are both over 6 years old and use the older style of pk before it changed in 2018/19)
but the current solution is not to change the difficulties, rather the route to take is rebalancing them to more consistently fit in one difficulty, efforts ARE being made to establish these edge cases (though they are on pause and are currently focused on insanes)
one side effect of this disparity to note is also what MAKES a map difficult and why some maps don't seem to fit the category: complexity, a lot of maps that feel too hard more than likely are also comprised of more complicated/technical jumps due to that shifting to be the style preferred for quite a while now, this has had a knock on effect on rendering the older style maps as a bad indicator of the difficulty due to their simple jumps styles naturally being easier for people, and i do agree archiving them to a legacy difficulty may be beneficial in the future, but not now.
the tl;dr of what you ask is simply: yes it should be done but it cant be due to many factors so rebalancing within the difficulty is presently the much easier option, this could be feasible though if they take the opportunity to rebalance AND rerank maps for the 1.20 update, but presently it is not an option.
