Now I understand.
That page is based on Squawk codes planes are showing.
As mentioned on top: Squawks: 06xx, 07xx, 25xx, 31xx, 40xx, 50xx, 53xx, 57xx, 66xx, 67xx, 72x, 7471-7479,7501-7535, 76xx, 77xx
Which means, if a feeder (worldwide) has a military aircraft which is using such a squawk is will be shown as a aircraft likely to work with Lippe.
But as you might have guessed by now, by no means it is 100% watertight.
So in this case a T-38 was using a Squawk in the USA which in our region could mean he is working Lippe. Therefore it showed as such