They do. But I am not sure how I can verify it. You can check it from here https://www.binance.com/en/proof-of-reserves
Instead of checking their own claimed proof of reserve, I collected their Bitcoin Wallet data. Check the data below

Address 1- https://blockchair.com/bitcoin/address/34xp4vRoCGJym3xR7yCVPFHoCNxv4Twseo 248,597.39   BTC
Address 2- https://blockchair.com/bitcoin/address/38Xnrq8MZiKmYmwobbYdZQ5nnCbX1qvQfE 117,351.06 BTC
Address 3- https://blockchair.com/bitcoin/address/38DN2uFMZPiHLHJigfv4kWC9JWJrNnhLcn 40,041.05 BTC
Address 4- https://blockchair.com/bitcoin/address/bc1qm34lsc65zpw79lxes69zkqmk6ee3ewf0j77s3h 38,802.05 BTC
Address 5- https://blockchair.com/bitcoin/address/3LQUu4v9z6KNch71j7kbj8GPeAGUo1FW6a 37,926.98 BTC
Address 6- https://blockchair.com/bitcoin/address/3M219KR5vEneNb47ewrPfWyb5jQ2DjxRP6 37,326.42 BTC
Address 7- https://blockchair.com/bitcoin/address/3FHNBLobJnbCTFTVakh5TXmEneyf5PT61B 31,275.35 BTC
Address 8- https://blockchair.com/bitcoin/address/3Qxak1CZhLyZ7GVckKphLURdLBCjMfz9bA 17,669.23 BTC
Address 9- https://blockchair.com/bitcoin/address/34HpHYiyQwg69gFmCq2BGHjF1DZnZnBeBP 16,306.63 BTC
Address 10- https://blockchair.com/bitcoin/address/36zSLdRv1jyewjaC12fqK5fptn7PqewunL 10,031.96 BTC
Address 11- https://blockchair.com/bitcoin/address/3EbJfpmFgufYtzW9UFvf1GAfm2ted1Rwnr 3,821.08 BTC

There are a few more addresses currently holding less than 3000 BTC each. These are the major Wallets currently holding 599,148 BTC.
All of them are on-chain. They also hold some Shitcoin like wrapped Bitcoin, Bitcoin on BSC chain etc etc.