Incorrect Information in Greek Alphabet Tutor?

It is correct. In modern Greek, delta is pronounced as th. 

https://en.wikipedia.org/wiki/Delta_(letter)#:~:text=6_References-,Pronunciation,romanized_as_d_or_dh.?wprov=sfla1 

It is correct. In modern Greek, delta is pronounced as th. 

https://en.wikipedia.org/wiki/Delta_%28letter%29#%3A%7E%3Atext%3D6_References-%2CPronunciation%2Cromanized_as_d_or_dh.?wprov=sfla1  

I've added a space after the link.

Just to be sure: delta should NOT be pronounced as the unvoiced th sound in English words like "bath", "thick" or "thin" (which is the modern Greek pronounciation of the letter theta). Delta is a voiced dental fricative like the th sound in "brother, "this" or "that" (you should feel your vocal cords vibrate when you put your hand to your throat).

Thank you for the reply. I understand that it is correct in modern Greek. There is a setting for modern Greek in the alphabet tutor. However, Koine Greek has its own setting and I was under the impression (from reading Basics of Biblical Greek on Logos) that Koine Greek had a "d" pronunciation. 

At the moment I am reading A Short Guide to the Pronounciation of New Testament Greek by Benjamin Kantor. Here is a screenshot from this resource:

Thank you again for your reply. If I am reading this correctly, doesn't this mean that the Koine Greek tutor should list the pronunciation as "d" rather than "th"? I think it is a safe assumption that most people using the Koine Greek alphabet tutor are attempting to learn Biblical Greek. 

Thank you again for your reply. If I am reading this correctly, doesn't this mean that the Koine Greek tutor should list the pronunciation as "d" rather than "th"? I think it is a safe assumption that most people using the Koine Greek alphabet tutor are attempting to learn Biblical Greek. 

No, Kantor actually recommends the same pronunciation as the Alphabet Tutor even though this was not the way that delta was probably pronounced in the first century AD. The same seems to be true for Randall Buth's reconstructed Koine Greek pronunciation.

Thank you again for your reply. If I am reading this correctly, doesn't this mean that the Koine Greek tutor should list the pronunciation as "d" rather than "th"? I think it is a safe assumption that most people using the Koine Greek alphabet tutor are attempting to learn Biblical Greek. 

I think the consensus is that the historical pronunciation of koine was very similar to modern Greek. They figure that out from spelling errors and things like that. Erasmian pronunciation is just a convenient fiction to make spelling easier for us.