Yes, of course. Processing takes much longer for many people, some consulates have 2 years + wait just for an interview so even if their category was current they wouldn’t have got a visa before it retrogressed.
As for why, it tells you that in the VB - "In the April 2023 Visa Bulletin, it was necessary to establish a final action date in the F2A category and Item D of the July 2023 Visa Bulletin warned of the strong possibility of retrogression as early as August. Number use has remained steady, and it has become necessary to retrogress the final action date to keep number use within the FY-2023 annual limit."
Hopefully it will move in October, good luck.