Nano - MTU doesn't apply for streams

The MTU parameter in the network page doesn’t seems to work/apply.
We need to reduce the MTU because we use IPSEC/GRE tunnels in the network path between the Nano and the receivers.

When captured using wireshark, the packets sent by the Nano are the same size regardless of the MTU set in the network page.
Here are the packet size we saw, with a MTU set at 1400:
MTU stream RTP : 1328
MTU stream UDP : 1316
MTU stream RTSP(TCP) : 1460
MTU stream RTSP(UDP) : 1472
MTU stream HLS : 1460
MTU stream SRT : 1332

The Nano we use is in version 4.24.0