Security tape isn't waterproof so water will eventually soak through, admittedly the drainage in the window should be able to cope with this but you need to make sure the glass packers ARE NOT obstructing the slots AND that they've used bridge packers too. It would be interesting to see if theres water sitting in there right now. Personally I'd still be inclined to refuse the work.
I would suggest my own work around to them, show them the credit card thing, suggest to them there isn't enough compression against the gaskets and that the units need to be thicker, OK the units might be 28mm which may be correct but thats assuming the beads are correct as well, it could be they've fitted triple glazing beads which stand a bit more upright allowing for a thicker unit, its a long shot, I don't know what size their triples are, could be 32,36, I even fitted a few 40's a few months ago for a colleague but they were into spectus. Suggest to them to replace a small unit as a test piece but make it 30 or 32mm, the 30 would need to be double glazed and have 6mm glass for one pane though, the 32 would need to be triple glazed with 4mm panes