For zoning lots in R8A Districts, or in Commercial Districts mapped within, or with a residential equivalent of an R8A District, within 100 feet of a wide street located outside of Mandatory Inclusionary Housing areas, the underlying height and setback provisions applicable to an R8 District within 100 feet of a wide street shall apply. However, sky exposure plane buildings shall not be permitted, and the additional height allowances for eligible sites set forth in Section 23-434 (Height and setback modifications for eligible sites) shall not apply.