I have indeed trouble with your question. I don't understand how "B b4-b3" or "B b3-b5" has anything to do with a bishop's moves.
You may be familiar with abbreviated algebraic notation, such as Bb3, which would mean to move a Bishop to b3. This abbreviated notation depends upon knowledge of the position and knowledge of the rules. Without these, you don't know where the Bishop is, and if a player has more than one Bishop, you don't know which Bishop to move there.
Since Chess variants are played by a variety of different rules, it helps to use a generic rule-blind notation that can work equally well for different variants. The notation I used explicitly spells out a move in a manner that someone could follow without knowing the rules of the game in question. First of all, "B b4-b3" is a typo. I meant to write "B b5-b3", which means a move by the Bishop on b5 to b3. This is a possible move only if there is already a Bishop on b5, and whether it's a legal move depends on the rules of the game. In Miller's Spherical Chess, for example, it would sometimes be a legal move. Likewise, "B b3-b5" means a move by a Bishop on b3 to b5. It should now be evident what these have to do with Bishop moves.
You may be familiar with abbreviated algebraic notation, such as Bb3, which would mean to move a Bishop to b3. This abbreviated notation depends upon knowledge of the position and knowledge of the rules. Without these, you don't know where the Bishop is, and if a player has more than one Bishop, you don't know which Bishop to move there.
Since Chess variants are played by a variety of different rules, it helps to use a generic rule-blind notation that can work equally well for different variants. The notation I used explicitly spells out a move in a manner that someone could follow without knowing the rules of the game in question. First of all, "B b4-b3" is a typo. I meant to write "B b5-b3", which means a move by the Bishop on b5 to b3. This is a possible move only if there is already a Bishop on b5, and whether it's a legal move depends on the rules of the game. In Miller's Spherical Chess, for example, it would sometimes be a legal move. Likewise, "B b3-b5" means a move by a Bishop on b3 to b5. It should now be evident what these have to do with Bishop moves.