To be fair, 'loads into memory' and 'stores' are not the same thing.
To fair though, there are very few situations where the network is completely trustworthy, like your home network with no one else on it or a VPN direct to an HTTP server.
A really really untrustworthy network could MITM your SSL connections and impose itself in front of all of them (Cisco IronPort?) but I think even then your browser will complain unless you've installed a proxy that allows it or a custom root certificate.
It’s not enough for the network to be untrustworthy for MITM attacks, they have to use a certificate signed a by root certificate that your computer already trusts.
Organizations with those IronPort gateways use device management and Active Directory policies to pre-install a root certificate into your OS. The IronPort decrypts the original server then re-encrypts it with its own certificate to your computer.
If you used a non-organization managed device on those networks, it would show big scary warnings before letting you visit any HTTPS site that the certificate issuer is not trusted by your computer.
I mean, sure, if you literally ignore the words "in memory", but by that logic you could argue that "Microsoft Edge stores" is misleading because it sounds like it's talking about retail establishments that sell the web browser, which is equally nonsense. I don't find it plausible that you think most people would see "stores in memory" would mean "stores on disk" unless you think that they don't understand the difference between memory and disk, at which point I don't think that they would be here to misread the headline.