Mortgage 1.65% 30 year fixed. I see these advertised. I'm 3.75% 30 year fixed and I am first time homebuyer. What gives?

I bought my home 5 months ago, first time homebuyer at a 3.75% 30 year fixed. I graduated loan officers and both my loan officers said these 1.65% 30 year fixed 0% down mortgages are all scams for first time homebuyers and they just want you in their pipeline. Does anyone know if 1.65% 30 year first charge mortgage is a real thing? And I'm not an investment property, I'm a first time homebuyer.<br><br>I even called one of these lenders and they hinted at it being an ARM but wouldn't specify. What makes my 3.75% loan so different from the 1.65% loan they are offering? I feel like I'm a month or two away from a decade-low rate and I just missed that and now I'm at 4%. I graduated loan officers and no one seems to know the answer to this question.