After planting the T-ENG post there, the area becomes sealed off after the time skip. This means that you can't empty the T-ENG post later in the game (which can be very useful once you have access to the other shop and upgrades).

Also, the specific cavern where you plant the T-ENG is supposedly the lair of the Suwankaa and Goonroes, or rather the Alpha Lair as it is called in the multiplayer map. I think this would have been a more fitting area to gather the samples of those two mammal-like Akryd.

Last, but not least, there's even a missable specialized component for the Utility Rig shop in Hanneman's Basin itself.

I would really like to know the reasoning behind such and odd design choice.

Many areas become sealed, but I at least hoped that T-ENG posts would remain accessible during the entire game in order to regularly drain them.