You’re assuming that the pineal gland is a third eye/dimensional gateway, then asking why God allegedly created it that way. Obviously the pineal gland has a purpose in the body, but there is no indication that this purpose involves spiritual enlightenment or dimensional travel.

You’re assuming that the use of this third eye brings you closer to God than prayer does. Through the sacrifice of Jesus Christ, those who are saved have direct access to the Father. Jesus is our intermediary. What makes you think there is something or someone better?

Just because stuff regarding the third eye has been taught for millennia, doesn’t mean it’s right. Appeal to Age/Appeal to Tradition fallacy.

Third eye practices are often viewed as demonic because it advocates focus being placed on the self. You work and do things to attain spiritual enlightenment using yourself as a guide. This is the opposite of biblical teaching as it is the Holy Spirit who works in us to draw us closer to God. And we are saved through the finished work of Jesus Christ, not extra work that you have to do to achieve “enlightenment”.

The Word of God is the sole and final revelation from God to man. Since God wrote it, it contains everything that you need regarding spiritual practices and your relationships with God. God didn’t leave anything out. “God is trying to hide knowledge from you” is the exact same lie that Satan told Eve in the Garden. Anything that advocates for any other source being on par with or surpassing the Bible is trying to draw you away from God, not closer to Him.