The transliteration is from ***ANCIENT*** Greek to modern English. This is not that difficult. These are not "trivial" or "nitpicking" problems, which implies that we aren't paying full attention or don't care about the details, when the extreme opposite is the case. While we might make mistakes occasionally, there is no skipping over lightly the transliterations.

sigma-phi-epsilon-nu-delta-omicron-nu-eta-tau-alpha-iota transliterates very clearly into:
s-ph-e-n-d-o-n-e-t-a-i

Classical Greek pronounces "phi" as an aspirated "p" ("top", where the "p" actually has a very very slight "uh" right after it), not as an "f". We will never have "Sfendonetai". And classical Greek has clear differentiation between a delta and a tau, which is very close to the differentiation between a "d" and a "t" in modern English.

Sphendonetai has a "nu-delta", where Akontistai has a "nu-tau". We will be keeping those as a "nd" and an "nt" respectively therefore. Foreigners mispronounce the *modern* Greek, Idomeneas, in the situation you point out. I totally agree with you there. But the ancient Greek is not the same.