hello, I'm doing some modelling to be integrated with live action and I am using real measurements. I realized that polyBevel sop doesn't work right on edges less than 0.056 units/meters. You can see the parameters that I'm using on the polyBevel sop and the result on the viewport on the attached image, the corner supposed to be round. Am I doing anything wrong or is it Houdini's problem?

I encountered this problem also.
I think it is a problem with precision, or the lack of it, and yes, it seems like a Houdini's problem.
As you can see, your value (0.004, which is 4 milimeters) is hard to handle, it's too small (to many decimals after the point), so the algorithm is lacking the precision to function correctly.
A workaround that I found is to insert a transform node before the polyBevel, scale the geometry to 100, do the bevel (it's value will be 4.0) and after that insert another transform node and scale everything back.
PS:
This is raising the question: Which unit is best for 3d work? Meters? Centimeters? In artistic 3d programs , which generally don't have the double precision of, let's say, Autocad, is best to keep everything close to 1 unit. So, if you have islands to model, work in meters or even kilometers. If you have skyscapers, boats, houses, work in meters. If you have small things, details, etc, work in centimeters.
In XSI the default unit 1=10 centimeters, which is a better compromise between meters and centimeters, precision wise.