The saddle on my new D1A is I guess beveled or "shaped" for the B string. When I strike the B string it has a slight buzz. Is that normal? Why do makers make this type of saddle? I was considering getting a new saddle that doesn't have that shape. On my D-18V it doesn't have that shape nor the strange buzz and I like it. Any advice?

The saddle is shaped to provide proper intonation on the B string, which tends to note sharper than the G or E strings.

Re the buzz: if you only get a buzz on the open B string, your problem is probably at the nut (i.e, too low or poorly cut). If you get the buzz only when fretting the string at a certain fret, your problem may be a high (or low) fret slightly higher than the one you are fretting. If the buzz is on every fret of the B string, the problem may be the saddle. Take the guitar to a good setup person, and they should be able to diagnose and fix the problem easily.

The first string that got buzz on my Collings is also the B String when the action is very very low, I do understand that a buzz especially on the treble strings is irritating but probably not caused by the compensated Saddle. And the B string on Collings, from my own experience, seems to buzz a little easier than other strings.

Did you buy you Collings used? The compensated Bone Saddle on Collings is not as shape on the B string as some others like those by TUSQ you normal found on Taylor Guitars etc. If your Saddle is not the original, may be its not probably installed.

If properly setup, your buzz will absolutely disappear. I recently lowered the action of my Collings to 6/64 Bass E and 4/64 Treble E measured from the 12 fret. I play very hard and got no buzz at all.

Check the relief as well. If buzz when fretted higher up, you saddle is probably too low. If buzz when fretted on first five frets, the relief is not enough. If buzz when played open, the nut is too low.