You can't set duplex/speed settings of the Fortigate interfaces?

Sometimes you can't set duplex/speed settings of the Fortigate interfaces. Important note: depends on which interface you are trying to set!.
Upon careful examination turns out that you can't set duplex/speed settings of 4-port switch interfaces only, i.e. Internal interface of Fortigate 60, 60M, 100A, 200A, and FortiWiFi-60 and also LAN interface of 500A .

Tried on FG100A FortiOS v4.0,build0178,090820 (MR1)

    FG100 (dmz2) # set speed
    100full    100M full-duplex
    100half    100M half-duplex
    10full     10M full-duplex
    10half     10M half-duplex
    auto       auto adjust speed

Working most of the time with Cisco gear I'm (and others) used to being able to set duplex/speed parameters on the physical interfaces to my liking. This comes as a necessity when connecting cisco to various equipment of differing quality. So it was a surprise to me when I encountered layer1/layer2 connectivity problem between some Fortigate 200A and Cisco router and tried to set manually duplex full/speed 100 on the Fortigate just to find out that it is impossible to do it on that Fortigate. It was possible back in the days of FortiOS 2.80 (and early 3.0 - I guess up until MR5)  :

# conf sys int
(interface)# edit internal
(internal)# set speed

    100full 100M full-duplex
    100half 100M half-duplex
    10full 10M full-duplex
    10half 10M half-duplex

But then Fortinet dropped this option and the only (not direct) explanation found on their site is this memo: "Locked-down port policies (forcing speed, duplex, and link capabilities with auto-negotiation disabled) are outdated. Legacy and historical reasons for forced setup with auto-negotiation disabled date back many years when the technology was new..."

Now we can see what is the negotiated status of the links (this command also shows errors/collisions/MTU on the interface) :

FG100 # diagnose hardware deviceinfo nic internal

    Description VIA VT6102 Rhine-II
    Part_Number N/A
    Driver_Name via-rhine
    Driver_Version 1.1.17
    PCI_Vendor 0x1106
    PCI_Device_ID 0x3065
    PCI_Subsystem_Vendor 0x3065
    PCI_Subsystem_ID 0x1106
    PCI_Revision_ID 0x74
    PCI_Address 0:12.0
    PCI_Bus_Type
    Memory 0x0000f400
    IRQ 11
    System_Device_Name internal
    Current_HWaddr 00:09:0f:30:32:11 #In HA set up primary member would have different , virtual MAC address 
    Permanent_HWaddr 00:09:0f:30:32:11
    Link up
   Speed 100
    Duplex forced full
    FlowControl off
    State up(0x00001103)
    MTU_Size 1392
    Rx_Packets 89944267
    Tx_Packets 73437299
    Rx_Bytes 370540924
    Tx_Bytes 428118992
    Rx_Errors 0
    Tx_Errors 0
    Rx_Dropped 0
    Tx_Dropped 0
    Multicast 8810
    Collisions 0
    Rx_Length_Errors 0
    Rx_Over_Errors -0
    Rx_CRC_Errors 0
    Rx_Frame_Errors 0
    Rx_FIFO_Errors 0
    Rx_Missed_Errors 0
    Tx_Aborted_Errors 0
    Tx_Carrier_Errors 0
    Tx_FIFO_Errors 0
    Tx_Heartbeat_Errors 0
    Tx_Window_Errors 0
    Tx_Single_Collision_Frames 0
    Tx_Multiple_Collision_Frames 0
    Rx_Frame_Too_Longs 0
    Rx_Symbol_Errors 0
    Rx_Control_Unknown_Opcodes 0
    Rx_Pause_Frames 0
    Tx_Pause_Frames 0
    Scatter_Gather OFF
    poll_intr_switch 0
    rx_tasklet_pkts 92505560
    xmit queue 0
    recv queue -64
    phy_id= 1/1

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