CC1352P: UART2_write() blocking for 200-500 us in UART2_Mode_NONBLOCKING

Hi ! 

SDK 6.41.0.17 + syscfg 1.15.0 + CCS 12.3.0.00005

I'm moving data from the radio to the UART in a low priority RTOS task loop. 
I'm noticing, using a GPIO toggle and a scope to time it, that UART2_write() is blocking my thread for 200-500 us.

Can you tell me if I have this setup properly? is 200-500 us normal for the non blocking API ?

void appUartInit() {
    UART2_Params uartParams;
    UART2_Params_init(&uartParams);
    uartParams.baudRate = 8*115200;
    uartParams.writeMode = UART2_Mode_NONBLOCKING;
    uartParams.readMode = UART2_Mode_NONBLOCKING;
    /*
     * UART2_ReadReturnMode_PARTIAL unblocks or performs a callback whenever a read timeout error occurs on the UART peripheral.
     * This timeout error is not the same as the blocking read timeout in the UART2_Params;
     * the read timeout occurs if the read FIFO is non-empty and no new data has been received for a device/baudrate dependent number of clock cycles.
     * This mode can be used when the exact number of bytes to be read is not known.
     */
    uartParams.readReturnMode = UART2_ReadReturnMode_PARTIAL;

    uart[1] = UART2_open(CONFIG_UART_0, &uartParams);

    if (uart[1] == NULL)
    {
        while (1) {}
    }
}

int appUartWrite(uint8_t *buf, int len) {
    size_t bytesWritten = 0;
    GPIO_write(CONFIG_GPIO_0, 1);
    UART2_write(uart[1], buf, len, (size_t *)&bytesWritten);
    GPIO_write(CONFIG_GPIO_0, 0);
    return bytesWritten;
}