No, you're thinking of Kraken, which has been doing this for years (not an endorsement!). Binance just did it, by revealing their wallet addresses, and promised more in future.

Two important points: 1. Generally Proof of Reserves is a term where all holders can validate cryptographically that their funds are accounted for. This is harder because it's natural and efficient for an exchange to co-mingle multiple customers. 2. Doesn't mean they're solvent! They might owe customers $100bn for all anyone knows.

It's still far better than nothing, but FWIW their history of lying about their home jurisdiction, and massive "out of nowhere" growth is a huge red flag that you should be aware of (FTX did the latter even faster, of course, being founded in 2019!).