I have Inspiron 5510. It also needs me to press power button for atleast more than 1 second (to be precise) to turn it on battery power, but on plugging it into charger it turns on with swift press of the button (same duration as needed during typing on keyboard).   This is Dell related design. They have designed it intentionally this way.
I recently purchased Dell Inspiron 3501 (i5 11th gen) model. It does not turn on like my other dell laptops by pressing the power button once. It needs me to press it for 2-3 seconds, however when it is plugged in, it turns on by a single press. I wanted to ask if this is normal. It was like that since the day I got it. The laptop runs fine otherwise everything is normal during operation. Please help me with this query. Thanks
Inspiron 3501, long press of power button to boot up