That would make things more clear and provide room for interpretation for other settings. However, don't mind a generic standard. Like everything in D&D I am happy to use fluff or not.
My gaming style treats fluff as rules − especially with regard to narrative adjudication. So for me, it is an endless nightmare to deal with 5e rules that constantly inject unwanted narrative rules (≈fluff) even within the mechanics themselves.
I don't think it is an oversight (it has been printed this way in 3 different books I think). I think in 5e deities are not a "type."
If a lesser deity isnt even listed as a tag, such as the case for Timat, then it seems conflictive when the rules list the quasideity titan as a tag. For the sake of consistency and clarity, it seems better to either remove the ‘titan’ tag from all statblocks, or alternatively change ‘titan’ into a special type, like Dragon and Giant. Alternatively, add various kinds of tags for other divine ranks, but actually, I would rather remove all references to polytheism from the core rules anyway.
In the meantime, I am happy enough to treat ‘titan’ as a race. The ‘titan’ race can reproduce by means of a ‘union’ or by means of being ‘manufactured’. For this reason, the race can become many different forms. So if the Kraken can reproduce by means of a ‘union’, I dont see a problem.
Note, according to the polytheistic setting, the origin of elves is from the blood of a deity: the race of elves themselves are analogous to the titan race, and the elves also became many different forms. Likewise, the origins of the dwarves were ‘manufactured’ by a deity. Accordingly, titans are merely a very powerful race.
I assume an Archfey counts as a ‘lesser deity’?
Anyways the rules for types and tags seem inconsistent at best.
In the end, I feel the best solution is to allow a type to also function as a tag when applicable. For example:
• a ‘Half-Dragon’ Half-Human is ‘humanoid (dragon, human)’
• a ‘Dragonborn’ is ‘humanoid (dragon)’
• an Eladrin is ‘humanoid (fey elf)’
• a ‘Tiefling’ is ‘humanoid (human, fiend)’
• a Faerie Dragon is ‘dragon (fey)’
• a Cuatl is ‘dragon (celestial)’
This approach allows the tags to truly be looser, and for the designer to mention whatever tag helps to clarify the relationship between one creature and an other.