yup. this is exactly what happened during the restore process. phone was on charge and it was restoring and updating around 100 apps. internet was extremely slow at the time.
i have a feeling that this is a software issue. samsung is throttling wifi to save on battery or something. BUT. they have had almost a year to optimize wi-fi on this phone.
october update might have a fix assuming they know about this issue. but it is currently available only in europe. it's unlikely india is getting it this week. would have been nice to test out wifi after installing it.