We ultimately don't know, unless someone goes after God about it. When I look at the Bible and look at my life, I'm inclined to believe that there aren't many mysteries God is unwilling to reveal. The one I'm sure He won't tell anyone (and I'm still not 100% sure) is the exact time of Jesus's return. Basically every other mystery is there for the revealing.
However, not everything God reveals to one person is supposed to be published to everyone else. Psalm 107:3 says, "He made known his ways unto Moses, his acts unto the children of Israel" (KJV) or "He revealed his character to Moses and his deeds to the people of Israel" (NLT). Someone wrote about this:
"What we see is that God made His ways known to and
revealed His character to Moses. In other words, Moses got to actually know God Himself. On the other hand, the people of Israel only saw His acts and deeds- what He did. Israel saw His works, but Moses saw God." (
https://www.jimandjanean.com/home/2019/6/2/his-ways-or-his-acts?format=amp)
Most christians, like most Israelis in Moses's time, are content to only know God's acts (ie. to be blessed, experience benefits from God, etc.) and don't want to get any closer to Him. People who want to know God's character, nature, or "ways" go after God for more. When He reveals things to them, some of those things are meant to be shared, but some are not.
"I know a man in Christ who fourteen years ago—whether in the body I do not know, or whether out of the body I do not know, God knows—such a one was caught up to the third heaven... He was caught up into Paradise and
heard inexpressible words, which it is not lawful for a man to utter" (2Corinthians 12:2, 4).
I believe God would be more than happy to reveal this mystery about sex in eternity. Afterall, when God hides things-- like Himself or things in the Bible and in Jesus's parables-- His intention is to reveal them. God is intelligent enough to make it so that the things He's unwilling to reveal never even make it into our consciousness (ie. we never even discover their existence). If there are colors, smells, animals in Heaven that we don't know exist, then we can't ask about them. But all the things that exist on earth (or the things we know about), we're allowed and encouraged to ask about and receive answers. If this wasn't true, then only christians would invent, discover, and solve issues. But God reveals earthly things to all people, not just christians. Therefore, He's willing to reveal even more things-- spiritual and secular-- to believers.