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I think the CFA curriculum probably uses theirs so that you can clearly see how the two parts (the beginning book value, and the RI) are separate. Otherwise maybe people would use the 1st formula and then add BVo while your formula does not require that addition. Also, (ROE-r)BV is the formula for RI, so it is easy to remember that way that the 2nd part of the equation is just RI/(r-g)
Just be careful not to get all of those mixed up with the formula for justified BV = (ROE-g)/(r-g)… They all start to melt together when they are similar.