Node Crypto Decipher Working Even With Altered AuthTag aes-256-gcm

Question

I have some code that does encrypts and decrypts a string using node crypto; however, when I pass in a different authTag into the decipher.setAuthTag, it still decrypts succesfully. I was wondering if this is the expected behavior. If not, what would be the proper way to authenticate the text has not been tampered with?

Standard Encryption:

const { createCipheriv, randomBytes, createDecipheriv } = require("crypto");
const text = "hello world";

const iv = randomBytes(16); // Initialization vector
const secret_key = Buffer.from(
  "2ef08b673cff8759d7df0546e8ff273415e072237c81c192ebe52ac1b10eb684",
  "hex"
);
const cipher = createCipheriv("aes-256-gcm", secret_key, iv);

let encrypted = cipher.update(text, "utf8", "hex");

encrypted += cipher.final("hex");
const authTag = cipher.getAuthTag().toString("hex");

const encryptedString = `${iv.toString("hex")}:${encrypted}:${authTag}`;

Standard Decryption:

const [iv_dcrypt, encrypted_dcrypt, authTag_dcrypt] =
  encryptedString.split(":");

const decipher = createDecipheriv(
  "aes-256-gcm",
  secret_key,
  Buffer.from(iv_dcrypt, "hex")
);

// Using a different auth tag
decipher.setAuthTag(Buffer.from(`${authTag_dcrypt}7`, "hex"));

let decrypted = decipher.update(encrypted_dcrypt, "hex", "utf8");
try {
  decrypted += decipher.final("utf8");
} catch (err) {
  console.log(err);
  console.log("Authentication failed");
}

console.log(decrypted); // No error is thrown and original message is shown