I also have the same issue.
First appeared after first service at approx 23hrs. As described a squeal at idle. Contacted the dealer. They seemd to not know what it was. So I even recorded it on HD camera and contacted suzuki direct. They immediately told me that it was the ceramic bush on the shaft which needed to be lubed. They did this under warranty and the noise disappeared... at least until we got to approx 50 hours. Same again. Took it back to the dealer and they "adjusted " the bush. Only made it worse and introduced a harmonic. The rep then gave them authorisation to replace the bush. Engine has now just done over 100 hours and the noise is back again. Contacted Suzuki they suggested to try another service agent. ( Which i will be seeing in about a week ).
I can start it in the morning and it will be quiet as a mouse. Run it at cruise speed for an hour or two ,pull back to idle and there it is again.

The engine hasnt even had its first birthday as yet.
I have never had an issue like this before with any other engine and have owned Hondas, Mercurys,Johnos/Evinrude, Mariners and even a Tohatsu.

I am not an expert but this sounds pretty fishy to me. I keep gettin the " we have never had one like this before" yet the net is full of them.

I suspect it might be the shaft itself. Perhaps the way its been heat treated or the stock it has been machined from. Under temp it warps slighty. Then damages the bush. (???)