Do I need full frame for background blur?

Here is what the site says about that.

From Portraits: Aperture and background blur: A wide aperture (a small f-number like f/1.8) gives a shallow depth of field: sharp eyes, soft background. Blur also grows with focal length, with getting closer to your subject, and with putting more distance between the subject and the background. Moving your subject away from a wall often does more than a faster lens. At f/1.4 and wider, the depth of field can be thinner than a face. Stop ...

From Sigma 105mm f/1.4 DG HSM Art: Sigma 105mm f/1.4 DG HSM Art: A prime lens by Sigma for Full frame cameras, 105mm f/1.4. A very large, very heavy portrait prime known for its background blur.

Quoted from this site's pages.