createPoolCluster does not maintain a connection to the same database throughout execution

when i call await execSQLFC(sql); then the problem occurs.
if i add await connection.query(USE ${process.env.SQL_FCDB}); it will working.
my configure (something wrong?):

****DBConfig.js

const mysql = require('mysql2/promise')

const poolCluster = mysql.createPoolCluster();

poolCluster.add('FloorcareDB', {
    host: process.env.SQL_HOST,
    user: process.env.SQL_USER,
    password: process.env.SQL_PWD,
    database: process.env.SQL_FCDB,
    connectionLimit: 50,
    waitForConnections: true,
    maxPreparedStatements: 500,
    queueLimit: 0,
    dateStrings: true,
    keepAliveInitialDelay: 10000,
    enableKeepAlive: true
});

poolCluster.add('TraceDB', {
    host: process.env.SQL_HOST,
    user: process.env.SQL_USER,
    password: process.env.SQL_PWD,
    database: process.env.SQL_TRACEDB,
    connectionLimit: 50,
    waitForConnections: true,
    maxPreparedStatements: 500,
    queueLimit: 0,
    dateStrings: true,
    keepAliveInitialDelay: 10000,
    enableKeepAlive: true
});

module.exports = poolCluster;

const poolCluster = require('../Config/DBConfig');

ExecuteSQL.js

const execSQLFC = async (sql, values) => {
    let connection;

    try {
        connection = await poolCluster.getConnection('FloorcareDB');
        await connection.query(`USE ${process.env.SQL_FCDB}`);

        console.log('Connected to FloorcareDB');
        const [dbCheck] = await connection.query('SELECT DATABASE() as currentDB');
        console.log('Current database:', dbCheck[0].currentDB);

        console.log('FloorcareDB');
        const [rows] = await connection.query(sql, values);
        connection.release();

        return rows;
    } catch (err) {
        if (connection) connection.release();
        console.error(err);
        return err;
    }
};

const execSQLTrace = async (sql, values) => {
    let connection;

    try {
        connection = await poolCluster.getConnection('TraceDB');
        await connection.query(`USE ${process.env.SQL_TRACEDB}`);

        console.log('Connected to TraceDB');
        const [dbCheck] = await connection.query('SELECT DATABASE() as currentDB');
        console.log('Current database:', dbCheck[0].currentDB);

        const [rows] = await connection.query(sql, values);
        connection.release();

        return rows;
    } catch (err) {
        if (connection) connection.release();
        console.error(err);
        return err;
    }
};

module.exports = { execSQLFC, execSQLTrace };

Start with the createPoolCluster and getConnection usage shown in DBConfig.js, then trace execSQLFC and execSQLTrace in ExecuteSQL.js. Reproduce the behavior with the two configured database names and compare the selected database before and after connection reuse. Done should include a confirmed cause and a focused regression test or documented expected behavior.