I'm guessing you're asking if you should remove the wall between the vanity and the closet in this room (?)..If so, are you asking if there's an esthetic rule of design regarding this situation?

Sort of. I noticed this photo while researching linen closets.

In my own master bath, I have a large open space along one wall. 6 linear feet will be shower and 11 linear feet remain. I thought about placing a vanity and linen closet in this remaining space. I noticed that some designers separate the linen closet with a wall and others just attach the linen closet to the vanity cabinetry. Since I am not constrained by space, I was curious on why some people add the wall separation.

TAke down the wall and add glass brick.

Where is the linen closets and vanity from

The wall in between makes it look like they originally had a regular old fashion closet there at one time. Without the wall is preferable.

Treat your long wall as for a kitchen, so each part is lined up, no wall in between.

This way it looks better as the Architect has defined the linen closet otherwise it would have been unending .

Defined spaces always look better in my opinion. This looks great the way it is separated.

If you had two linen cabinets flanking each side of the vanity, and have the vanity recessed a few inches behind the two linen cabinets, it may work, but this is the only way I would connect to a linen cabinet.

As is is fine! Only suggestion might be to either carry the cabinet to the ceiling or drop the ceiling to the top of the cabinet. The space above the cabinet looks a bit "empty", but I understand that the existing ceiling is what it is.