The Borer patrol periodically announces they caught five or ten of them who were on the watch list. They never detail the split between walk up's vs caught skulking in the desert. Don't see how that matters. The point is they are present in the population and pose a danger to us, more-so the more you let in, it's a numbers game.

It matters, because while it is plausible that someone might want to sneak into the country, it's implausible that they would voluntarily submit to the asylum process rather than other alternatives (like flying in on falsified documents). Which makes it exceedingly unlikely that any Administration could convince a judge that suspending the asylum process is necessitated by a national emergency. Which is why even DJT didn't do that, even as he was claiming a national security need to impose other "travel bans" in 2017 and 2018. Because it's implausible that you would allow the massive and extensive amount of entry through airports and seaports, but find the asylum process too porous. Because again, unlike travelling through ports of entry, an asylee is not only evaluated by federal officials also, but is subject to immediate and indefinite detention for any reason at all for as long as the government wants.

There's no way you could convince a judge that asylum applicants (as opposed to people sneaking across the border who just get deported when they're caught) pose a greater likelihood of containing bad guys than any other mode of entry.