STM32F413 product page says:
Up to 5 SPI/I2Ss (up to 50 Mbit/s, SPI or I2S audio protocol), out of which 2 muxed full-duplex I2S interfaces
Similar text can be found at the beginning of datasheet. The I2S chapter, though goes even further, explicitly stating (DocID029162 Rev 3, 3.26 Inter-integrated sound (I2S)):
Five standard I 2 S interfaces (multiplexed with SPI1 to SPI5) are available. They can be
operated in master or slave mode, in simplex communication mode, and full duplex mode
for I2S2 and I2S3.
Besides that I have no idea what "muxed full-duplex" might mean, I can't find a single mention of full-duplex I2S in RM0430 rev.2; contrary, the I2S subchapter is very specific in that it's half-duplex only.
ST, can you please comment.