Will have to disagree on this particular aspect, brother.
Because:
1) In principle the author in question is following Iranian naval developments (particularly in the submarine department) closely enough not to miss major news releases about sonars.
2) You might have forgotten that Iran unveiled the advanced Soroush sonar in July 2016.
سامانه سونار سروش با حضور فرمانده نیروی دریایی ارتش جمهوری اسلامی ایران در شیراز رونمایی شد.
www.mashreghnews.ir
Yet the author's cutaway of the Fateh submarine, still depicting the older sonar type, was published on his website on 16 September 2020:
While in his article dedicated to the Fateh-class, the author has included a photograph of the older sonar, adding the following caption:
An Iranian made circular sonar array consisting of vertical staves. This layout is similar to WW2 and 1950s Soviet designs.
View attachment 670970
The author did not update the picture, nor complete his presentation through the addition of an illustration of the Soroush sonar shown above.
This leaves two potential explanations:
1) He simply missed the news releases about the Soroush. However, wasn't the Soroush revealed at the same time as IRIB broadcast their report about Admiral Sayyari inspecting the interior of the Fateh submarine, which the author has included screenshots of in his article? Either way, this doesn't seem to be the most likely explanation.
2) He is aware of the Soroush but chooses not to mention it, subjectively considering there is "no proof" that it was fielded, or even believing that it constitutes "propaganda".
This is a common issue with western analysts of Iranian military affairs. They as good as always display a degree of bias and will apply differential treatment to Iran, for no other reason than the fact that the regimes ruling over their countries of origin and/or of residence, are hostile to Iran and to the Islamic Republic. Or in other words, the dominant, western regime-sponsored narrative (or shall we say, propaganda) overwhelmingly antagonizes Iran and so analysts are led if not compelled to follow suit.
This is why when several possible hypotheses offer themselves to them, they will almost systematically tend to choose the one which presents Iran in the least favorable light, the one most sceptical of domestic Iranian achievements. In the present case, there is actually more reason to believe that the Soroush sonar has effectively been brought into service rather than to assume it hasn't. But since Iran published no direct photographic documentation of the Soroush sonar inside a Fateh class submarine, the author will use it as a justification to postulate Fateh is still using the old sonar.
That still doesn't justify total obfuscation of the new sonar by the author though (in his article, he makes no mention of it whatsoever), especially if he is going to make sure to include qualifications such as "WW2 design" when referring to older Iranian-made sonars.