Sealed Sleeves in Basement Floor

I came across these items in a basement last week, and was looking for input. I believe them to be sleeve’s that were placed in the foundation to later remove and pour footings for jack posts that were never used due to movement of the overhead support beams. I spoke with a structural engineer and he believed the same, but I was wondering if anyone else has run across these. Thanks for your input.

What is the age of the home? How were they sealed? What is their location in the basement? Have a pic of the general area in the basement? My first thought is for future Radon Mitigation system.

That would have been my thought also, but they are located in two different places and they are out in the middle of the floor, not near the wall like most mitigation systems. I cannot reach down into the bottom of them, but they appear to have a cap in the bottom of them. The home was built in 05. One of them is directly in line with several other posts the other is off on its own. Would love to be able to find out from the builder so that I can tell the buyer something.

Those look like the threaded covers for backwater valves.