ok, it is this:
I’ve inspected in more detail the AuavX2 board, I especially looked at the signals on the pins of the Max3051 transceiver (which according to the AUAV_X2_R01.pdf scheme is what it should be), and from the signals on the RXD and TXD pins I concluded that they are in wrong order! A subsequent more alerted peek into the scheme in fact shows exactly this, namely that Can1Tx is connected to RxD and Can1Rx to TxD !!!
As a proof I soldered wires to the Max3051’s RxD and TxD pins (delicate solder job LOL) and connected them via my pseudo transceivers (I do not have enough transceiver modules around) to my slcan adapter and ran the GUI Tool … et voila, I do see now what one expects to see !!!
I must admit there had been once a time there I considered the Auav stuff high quality, but I stopped thinking so a while ago, and this is now really a most dismaying discovery. 
If there would be at least an errata sheet.
Anyway, I guess I have to dissolder that transceiver chip and produce some clumsy workaround … good I bought a high-quality board (and in fact two of them) …