Ground elder growing tubers?? Or wrong ID?

When digging holes on my clay slope to plant my fruit trees last February, I came across dozens of small penny sized (or slightly larger) tubers that resembled potatoes somewhat in skin and colour.
Being curious as to what they were, I took some home with me and threw them into a pot on my balcony to see what would come out. I’ve been anxiously looking at what would grow, given that it looked like my slope was full of these tubers. I was slightly disappointed to see that something suspiciously looking a lot like ground elder popped up. Don’t get me wrong, I like ground elder to eat, but the thought of the whole slope where I intended my orchard and veggies to go, being completely covered with ground elder, is slightly horrifying.
In any case, the more I thought and researched about it, the more confused I got, because I can’t find anything about ground elder growing tubers...
Do I have my ID of the plant wrong, or is there a rare situation or variety in which ground elder grows tubers? I can imagine that if the ground elder does seem to grow tubers, that tells me something about my soil?

This is ground elder as I know it. It does form nodules underground, but not the size of a penny - at least not here in Germany.
I would dig the pot up to see if the ground elder actually originated from that tuber you found.

Hi Anita,

I’m fairly certain they came from the nodules, as when I planted them, one of them already had a bit of green leaf sprouting. Unless the soil that was attached to it hid the fact that the roots of the ground elder had simply grown around the nodule instead of coming out of it?
In any case, I will try to dig up the nodules this weekend to see what is happening.