Anyone Try a Kessil A150 LED with Gooseneck on a Rimless Tank? I heard that you can't

So I want to set up a Frag Tank that would be 30 Gallons (30 X 18 X 12).



I have a Spare Kessil A150 LED so I was going to use that for Lighting so I would not have to buy New Lights.



Then I thought it would look better if I went Rimless without the Traditional Black Trim.



But My LFS said you could not do that because you would have The Metal Bracket from the Gooseneck touching Glass which would be a big no no.



So my question is has anybody tried this with Success? (or Failure).



And if so what happened.



What was Good or Bad with using a Kessil Gooseneck on a Rimless Tank?



Also, why is Metal touching Glass a Bad Thing?



Would it somehow Break the Glass?