I just tried to verify your point. Not to flood here, but to clarify things for other newcomers like myself:

🟡 I created a wallet on testnet and put some coins in it. Then, tried to delete the account on Tonkeeper Web. Also, imported the wallet on the mobile app and tried to delete the account there. And during the whole process, controlled the status via tonscan. Even when both wallets were deleted, I was able to send some amount to that address successfully, and the transaction was visible in tonscan.

➡️ Result: In all cases, the wallet was deleted APPARENTLY ONLY FROM THE LOCAL DEVICE. No change was observed on the blockchain (via tonscan).

➡️ Conclusion. Actually, I couldn't distinguish (with certainty) between this behavior of the "delete account" option in Tonkeeper and that of "sending a message with mode 160," which, as @Gusarich explained, modifies the data on-chain (which is still vague for me as I haven't experimented it yet).

Perhaps I had to wait for, say, more than 1 week to observe different results? Most notable of all was the ability to send money to the wallet even after deletion which is an indicative of the active state of the wallet.

PS: To get a clearer picture, I tried to search any kind of delete command within ton-blockchain.github.io/docs, but I couldn't spot the relevant material unfortunately. Also, looked at
https://docs.ton.org/develop/smart-contracts/messages#message-modes
which describes mode 160. Here, it seems that mode 160 must be something different from "delete account" in Tonkeeper.