Outer tread wear / worn sipes bad for wet weather driving?

May 20, 2022
I went into discount tire to have my TPS reset. I commented that I was aware that my tread depth was for 4/32 and probably on the cusp of needing new tires and the associate commented that the outer tread was worn devoid of sipes and my wet weather traction was now zero.

Obviously comparing brand new tires with my worn ones (I've see the consumer reports video) we would see that I would have less ability for the water to be pushed away due to the height of the rubber but I wasn't aware that the outer sipes designed into the tires had anything to do with wet weather traction - that's for snow and cornering - me thinks he was speaking out of his arse – was I correct?
I don't think the two are related.
But TBH I 'm not certain what the sipes on outer edges are for. Summer tires have a more solid block tread pattern, and the outer edges are nearly flat for a reason as well.
He may have just been saying that your tires are worn to the point where the wet performance is nil.
I still have grooves in the tires so it's not like I'm running F1 racing slicks :) I think he was trying to sell me new tires, fair enough but not by give me a BS reason, 4/32 is basically the wear limit recommend right ....

from tire review.com

At what tread depth should tires be taken out of service? For a long time, the standard answer has been 2/32-inches, but some in this industry are pushing for 4/32-inches. For good reason.

In Europe, the conversation has gotten pretty heated among tire manufacturers. Here, it is a barely audible conversation. So it comes down to what’s right for your customers.

Continental has come out strongly in favor of the 4/32-inch standard. The tiremaker states passenger tires should be “removed from service” when worn to 4/32-inch.

According laws in 42 states, tires are legally worn out when the tread depth is worn down to 2/32-inches (1.6 mm). There is no federal standard for con- sumer tires.

For commercial trucks, the federal limit is 4/32-inches for steer tires and 2/32-inches for all other positions
I use 2 to 3/32 in dry weather and 3 to 4/32 in the rainy season. Tire manufactures would try to get 6/32 as the standard if they could. Some of the better tires have sipes that go deep to the base rubber and lower quality tires have sips that only go ~ 1/2 way deep. Just my observations. Ed
We dont know if you live in the desert but in an area where you have regular rain 4/32" begins to get dangerous if you like to keep up with traffic on major highways while it's raining. In Mn I would be replacing those tires, in Arizona or some other desert state I'd run them.