I have just repeated the experiment. (In fact we have conducted it here previously.)
I do not get results anywhere near an intolerable 10ms. I find latency across presets in the neighborhood of 2.2 ms.
For the UNALTERED DoubleVerb (factory preset 1-1) with all its effects running, I get a latency in the neighborhood of 2.2 ms.
For the UNALTERED Badger 18 (factory preset 1-4) all its effects running, I get a latency in the neighborhood of 2.2 ms.
To perform this test, I use Logic and my RME Fireface UFX.
1. I set the hardware and project at 96k to ensure high resolution data and prevent the illusion of sample shifting.
2. I place a 96k audio test file on track 1, sending to output 1+2 as a stereo pair.
3. I connect Output 1 directly to Input 5. I mute the monitor for this input.
4. I connect Output 2 to the AX8 Instr. input. I connect the AX8 output 1L 1/4" to Input 6.
5. In Logic, I create a new track and record Input 5+6 as a stereo pair while playing back my test file.
6. I export the recordings and open in Sound Forge for close inspection.
7. By eye, I select the start point of the reference and the start of the AX8 signal. Note: I recognize that at this step there is the possibility of errors in the range of 0.00001 seconds (1/10th ms).
8. Sound Forge displays the duration of my selection in seconds (highlighted in a pink box in the PNG files attached): 0.002240 and 0.002229