I suspect that the original mono LP was released in April 1966, and the August date is for stereo overdubs or re-recordings. ISRC search on this barcode gives release day as 28th May 1991, which was a Tuesday, so that would have been the US release day. The catalogue numbering follows the US Atco system (it would have been 91705-2 there), so although the other Redding albums were released the same day in the US, that wouldn't necessarily be true for Europe or the rest of the world; Australian release was on 5th August 1991.
There are temporal distortions in the notes of this release worthy of an episode of "Star Trek"!! If the notes are to be believed all but 2 tracks on here were recorded in August 1966 but the original LP was released on 1st April 1966.
The original LP debuted on the BB "Pop" LP charts on 30th April 1966 and peaked at #54 during a 29 week run, on the BB "R&B" chart it debuted on 7th May 1966 and peaked at #5 during a 28 week run, so the stated release date on 1st April 1966 looks entirely credible.
As the catalogue number of this is consecutive with the re-releases of Otis's "Dictionary Of Soul" and "Sings Soul Ballads" in this series presumably they all came out on the same day?