You may have seen this practice of additionally suffixing BDD names with '.bdd' in many of the Webel IT Australia SysMLv1 examples. The same optional tip can be used for SysML Parametric Diagrams (using '.par' as suffix) and other Diagram types that might clash with the IBD when the IBD has the Block name (which in the Webel recipe is taken as the default).
If you are not exporting images from your SysMLv1 model you can safely completely ignore this tip.