I have found with the bottle and the tube being so flexible, I have to adjust my technique for a much lighter touch.
The bottle will certainly spin in my fingers without the right amount of pressure, which is very little without deforming it due to the ultra softness, think charmin tripple waves.
I hold the mod at different angle when refilling with these also, as the tube is so flexible, I can pull the bottle out at 90° with no real resistance, so doing that free's up space to hold the cap with the mod horizontal , front of the mod facing the ground, and screw the bottle vertically onto the cap.
A learning curve for me yes, but it has been a short and worthy one.
I have one parked in all my reos at this point, as I've been swapping at each bottle fill...
Time will tell if I keep this setup or go back to stiffer tubing and older bottles, but I have a feeling once it becomes second nature I won't know how I managed before

Your results will most likely vary.
Thanks Karen for sharing your experience so far.
I did fit an oring on the cap based on feedback from above, but I don't need it.
I like the cap just as it is, clean, machined, smooth. No problems for me to report.