I understand that you are looking at an issue where Antenna Port 4 is not able to be mapped using the "ltePDSCH" function via the "TxScheme" property. The reason why you cannot map to Antenna Port 4 is due to the specifications in the LTE Standard. Specifically,
3GPP Spec #36.211, which the link you provided:
is referencing to "MBSFN" signals as follows:
"MBSFN reference signals shall be transmitted only when the PMCH is transmitted. MBSFN reference signals are transmitted on antenna port 4."
However, PMCH (Physical Multicast Channel) is not the simulation target for the "ltePDSCH" function. Instead, the "ltePDSCH" function simulates "Physical downlink shared channel" (PDSCH). In this case, the specifications referred herewithin are:
 3GPP TS 36.101. "User Equipment (UE) Radio Transmission and Reception." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: https://www.3gpp.org/ .
 3GPP TS 36.141. "Base Station (BS) conformance testing." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL:https://www.3gpp.org/.
And the "ltePDSCH" function fully conforms with the appropriate specifications.