So you think you understand IP fragmentation?

That's the MAC MTU; the PHY MTU can be as large as 2,097,148 bytes in 802.11ac networks (noting that the PHY MTU depends both on static parameters like channel width, but also dynamic parameters like time it will take to transmit the frame). For 802.11ax, the PHY MTU is permitted to go as high as 6,500,631 bytes. Even as early as 802.11n (in 2009), the PHY MTU was allowed to go as large as 65,536 bytes under good conditions.

This is made useful with a much smaller MAC MTU by having aggregation options, so that a single PHY frame contains many MAC frames; the downside is that there is overhead for each and every MAC frame in the PHY frame, which would go down if the MAC frames were larger. There would still be overhead mapping MAC frames into PHY frames, so you wouldn't have as large a MAC MTU as the PHY MTUs, but there would be large MTUs involved.