`hci_inquiry` seemingly ignoring `lap` parameter

Question

I'm doing some experiments with bluetooth on linux (Arch Linux), and apparently the lap parameter that I'm passing to hci_inquiry is being ignored.

With the following code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/hci_lib.h>
#include <bluetooth/l2cap.h>

int main(int argc, char** argv) {
    inquiry_info *ii = NULL;
    int max_rsp, num_rsp;
    int dev_id, sock, len, flags;
    int i;
    char addr[19] = { 0 };
    char name[248] = { 0 };

    dev_id = hci_get_route(NULL);
    sock = hci_open_dev( dev_id );
    if (dev_id < 0 || sock < 0) {
        perror("opening socket");
        exit(1);
    }

    len  = 3;
    max_rsp = 255;
    flags = IREQ_CACHE_FLUSH;
    ii = (inquiry_info*)malloc(max_rsp * sizeof(inquiry_info));

    uint8_t lap[3] = { 0x00, 0x8b, 0x9e };

    num_rsp = hci_inquiry(dev_id, len, max_rsp, lap, &ii, flags);

    printf("%i\n", num_rsp);

    free( ii );
    close( sock );
    return 0;
}

When I run this while capturing the bluetooth interface communication with Wireshark, I see that the inquiry is being sent with a LAP of 0x9e8b33, no matter what I pass as lap.

I'm trying to understand: why is this parameter apparently ignored? And how could I make it send the inquiry using the given LAP of 0x9e8b00?

EDIT: Using libusb to claim the USB Bluetooth adapter and directly send the Inquiry, I managed to make it issue inquiries with the correct LAP. So the adapter I'm using is perfectly capable of issuing such inquiries. I still don't know however why the controller seems to ignore/override the LAP when using hci_inquiry and how to do so without taking over the whole USB BT adapter.