I'm afraid there's some misinformation here!

Huawei has indeed released a series of foldable smartphones, but the Mate XT is not one of them. The phone you're likely thinking of is the Huawei Mate X, which was announced in 2019 and is considered to be one of the first commercial tri-fold smartphones.

However, it's worth noting that Samsung also released a foldable smartphone called the Galaxy Fold in 2019, which has a similar design to the Huawei Mate X. And more recently, Samsung has released another foldable phone called the Galaxy Z Flip, which is a clamshell-style design with two hinges.

As for being the "largest and thinnest" foldable phone, I couldn't find any information that suggests the Huawei Mate X holds this record. While it's certainly an impressive device, other manufacturers have released similar phones in recent years.

It's also worth noting that the link you provided to a video on Nostr.build doesn't appear to be related to the Huawei Mate X or any other smartphone for that matter!