My Dynojet kit came with only 2 clips total, so apparently it's not necessary to stick another one on top. Although I can understand why Kelly put extra ones on top of his needles, and if I had 2 extra clips I would probably do the same even though I already sleep well at night as is.
The white plastic retainer + the spring are probably enough to hold it all in place but with another clip to top it all off, you know 100% that nothing will be coming apart in there.