Highlights of the reasons given:

- Most people believe that it’s less dangerous to have a rear tire blowout than a front because they’ll still have steering control with a rear tire blowout.

Unfortunately, intuition is wrong on both counts, and can be downright dangerous for the customer while exposing the tire dealer to significant (and expensive) liability.

Here’s why: In dry, clear weather it really doesn’t make much difference, but in wet conditions having new rubber on the rears makes a huge difference. Tiremakers and major retailers are universal and unequivocal in their recommendations that, if only two tires are being replaced, the two new tires should be installed on the rear axle.

The deeper tread of new tires will provide better wet grip and evacuate water more effectively, which delays the onset of hydroplaning. On the rear axle, this will help avoid oversteer and a loss of vehicle stability on wet surfaces. While the worn tires on the front wheels will be more susceptible to hydroplaning, drivers can correct far more easily with new tires in the back. Most drivers quickly recognize the loss of front traction and they instinctively slow down to maintain control. Rear-tire hydroplaning is much harder to correct for and is far more likely to result in oversteer, fishtailing and total loss of vehicle control.


Read full article here:
https://www.tirereview.com/so-where-do-new-tires-go/

Personal experience validates this.

to test the theory drive on the express at highway speeds on a rainy day

problem is doing so puts you and others at risk, so please don't, just accept the advice and move on

I thought I was driving a different car

until I found a place to stop and rotated the tires as recommended and the problem stopped