You quoted both upgrades of Tear of the Goddess twice (Archangel's staff + Seraph's embrace in AP, Manamune + Muramana in AD), Hextech gunblade in AP only even though it gives AD as well, Wit's end in AD although it deals magic damage and can be used by pretty much any champion that basic attacks frequently (i.e. Kai'Sa, Jax, Shyvana... all of which can deal high magic damage), Executioner's calling in AD although it isn't a complete item (might as well write down Lost chapter, Aether wisp, Oblivion orb etc. if you want to play this way), and you didn't list jungle items, Frozen mallet, Iceborn gauntlet (deals physical damage), Mejai's soulstealer, Guinsoo's rageblade, to a certain extent Remnant of the watchers since it can be bought by a number of AP supports (and gives AP by the way), plus Abyssal mask since it increases magic damage dealt to surrounding enemies. I will add that Ekko and Zoe for example can buy a Rapidfire cannon, too, for extended attack range, with maybe other borderline cases that I forget. It sounds a bit faulty of a rant to me.
As far as diversity is concerned, top row has mana regen, heal (Athene's unholy grail), shield on self (Seraph's embrace), empowered heals and shields, attack speed buff (Ardent censer), AoE damaging dash ability (Hextech protobelt 01), AoE damage and slow ability (Hextech GLP-800), multi-target damage (Luden's echo), single-target damage and slow ability (Hextech Gunblade) on an item that also gives universal vampirism, percent maximum health damage over time (Liandry's torment), spell shield (Banshee's veil), bonus damage after using an ability (Lich bane), grievous wounds (Morellonomicon), slow on abilities (Rylai's crystal scepter), health and mana recovery by fighting (Rod of Ages, Abyssal mask), team-wide movement speed buff (Shurelya's reverie), stasis (Zhonya's hourglass), AP and movement speed buff on self (Spellbinder), long-range scouting and slow (Twin shadows), on-hit damage (Nashor's tooth).
Some of these have no equivalent in your bottom row's items, such as the buffs, various debuffs (except for the single-target slow of Blade of the ruined king), dash, stasis, spell shield, on-demand shield burst. Sure, items that give AD seem to have a number of cool passives, but I doubt that e.g. an item restoring mana on hit (Essence reaver) would be considered healthy for a number of mages, reason why Morellonomicon was reworked.
While I agree that some options are a little over the top (cleansing a stun for example is like pressing the "second chance" key, which makes me wonder sometimes why exactly I can't have the initiative when I am the one engaging on a squishy damage dealer), overall I don't feel like AP characters were forgotten as far as items are concerned. Some items that you classified as AD include passives like "hit harder" (Trinity force, Infinity Edge) or "survive longer" (Sterak's gage, Maw of Malmortius, Phantom dancer), which feel pretty bland to me; nothing quite like a supplementary dash or an AoE slow, which both are meaningful enough.
As such, I still have no clue about any kind of favour Riot would do to one or the other side of the balance.