Warming up and cooling down are not that important. why is this inaccurate?

muscles do not need to gradually receive increased blood flow.

the above three options are why this is inaccurate. making time to warm up/cool down, gradually activating muscles groups to efficiently acclimate to the intended activity parameters, and slowly increasing and decreasing the training heart rate is important for heart health and efficiency. (just because this is a long answer does not mean it is correct ; ) )

the heart is strong enough to increases its rate and decrease its rate very quickly without being affected.

quickly completing an activity is more important and warm up/cool down takes too much time.