Any filter that is marketed as being suitable for any purpose should have some kind of evidence rather than claims.
In the absence of the
micron rating based on x%* single-pass efficiency (which might be a bit much to expect in Lambretta World

) then the screen size of any filter is the next best thing.
I have had to resort to DIY manufacture of my own filters & I use foam. I buy the stuff in sheets but they are relatively cheap......but @ least I know the screen size!
I may have missed the facts if they are stated about BGM's filter but, if I were you, I'd ask them.
IMHO the product looks too course & despite the claims, I would not use one without some proof of something measurable so that an informed choice can be made.
* x% might typically be 98%