According to the below review, no, they should not be used, Tamiya got that part wrong.
"Unfortunately, Tamiya misidentified a late M4A2 with appliqué armor as an M4A3. The appliqué armor was welded to the hull sides of the M4A2 to provide added protection to the ammo stored within. But the hull in this kit is the intermediate style with wet stowage (i.e., the ammo was stowed in a bath of ethylene glycol, or antifreeze). So don't use the appliqué pieces as the kit instructs."
From US Army Models website: www.usarmymodels.com/.../tamiya35122.html
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