SNES version - The back row bug for this version of the game is simple. If you equip a back row compatible weapon on a character, 
it is not unset when you switch to a non-back row compatible weapon.

This bug is very beneficial except that most of those weapons have the "disable critical bit" enabled which is the tradeoff. This 
bug occurs for all versions w/o exception.

Note: The "disable critical hit" bit is only available in the SNES version.

Characters that are unaffected are Tellah and Yang, since they do not have a back row compatible weapon.

Characters who are automatically inflicted with this bug include Rosa (initially) and Rydia (when she comes back).

Edge needs both hands to have equipped (at one point or another) a Boomerang weapon to take advantage of this bug.  This also 
implies that both hands need to be "back row" compatible for the benefits to stick when both hands have a weapon. This is the 
same reason why bows+arrows have that bit set.

GBA Version - There are two different back row bugs.

GBA US Version (probably includes Jap v1.0) - The back row bit is not adhered to at all, thus making normally back row compatible 
weapons to decrease hit rate.

GBA Euro Version (probably includes Jap v1.1) - The back row bit is not adhered to at all, thus making the either row deal the 
same amount of damage. The back row bit is effectively useless in this version.

What I've learned from all of this:

Back row incompatible weapons reduce hit rate by 1/2.

Attacking enemies that are "considered" to be in the back row also reduce hit rate by 1/2. This penalty is stackable with back row 
incompatible weapons.

Note: There is no front/back rows for enemies in FF4A. (In other words, there is no distinction for enemy location when attacking).

Second Note: Whoever spread the rumors that FF4ET didn't adhere to rows was grossly informed and didn't do any testing. More likely 
than not, they were experiencing the back row bug.

Back row compatible weapons (and those characters that are affected by the bug) in the SNES version are not affected by either back row penalty.

The GBA versions can't decide between "no back row compatible weapons" (US and Jap v1.0) and "always back row compatible" (Euro and Jap v1.1).

The Bow+Arrow combo is "bugged" in FF4A... I could be wrong if it is a bug, but I'll call it that anyways.

I originally thought Rosa's Attack command is tied to some character specific code that cripples her usage of the Bow+Arrow combo, to force the 
use of Aim.

However, that isn't the case.

Apparently, the back row bit is ignored when a Bow+Arrow combo is equipped.

All Bows and Arrows have the back row bit enabled. When testing this in battle, it appears that being in the front row does make a difference.. 
as full hit rate is available. In the back row, approximately half of the damage is dealt (which means 1/2 hit rate penalty is applied).

So, in conclusion:

To deal full damage with the Bow+Arrow combo in FF4A, you need to one of the following:

1) Have the Aim command, so you can use it effectively in the back row.

2) Be in the front row.