It would need a very specific context for situation tragedy to be considered an acceptable collocation.
The same kind of noun adjunct usage is well established in, for example, kitchen sink drama (where the noun kitchen sink identifies a specific sub-category of drama). Note that in context, a situation comedy would be understood (a comedy TV program, play, or film where the humour primarily arises from some unusual / amusing situation).
It's worth pointing out that strictly speaking a situation tragedy is "oxymoronic" (juxtaposes two incompatible elements)...
What is Tragedy? (literaryterms.net)
Tragedy is a genre of story in which a hero is brought down by his/her own flaws, usually by ordinary human flaws – flaws like greed, over-ambition, or even an excess of love, honor, or loyalty.
If it's the situation that brings misfortune, it's not really "tragedy". That might be part of the reason situation tragedy has little to no currency. Also note that some "purists" don't even like this kind of noun adjunct usage of situation anyway - they prefer the explicitly adjectival form situational comedy
(which we can't do with idiomatic kitchen sink drama, because kitchen sink doesn't have an explicitly adjectival form!).
Also note that no-one would seriously object to the default "adjective + noun" form a tragic situation simply because of the above (primarily, literary) definition. The meaning of tragic in normal contexts extends far beyond a specific sub-category of ancient Greek drama.