If you are about to go on the offensive and the enemy figures out where you are going to attack, it gives the enemy an opportunity to reinforce and fortify the point where the enemy is going to attack. The mobiks have no say in any of this. They are just the poor saps who get killed when the offensive begins.
At Kursk in 1943 the Germans did not do anything to really conceal they were about to launch a large offensive on the Kursk salient. Zhukov heavily reinforced the area and when the Germans did launch their attack the Russian defenses cut the Germans to ribbons. It was a hard fought battle with high casualties on both sides, but it marked the last large scale German offensive in the east and the second to last large scale offensive of the war (the Ardennes operation in late 1944 was their last major offensive).
If the Ukrainians want to keep operational security they won't use the Abrams for any major offensives. I would use them for a feint. Take the handful of Abrams and drive them around at night near one of the possible offensive points and get the Russians thinking the Abrams must be the point of the spear. Then launch the offensive elsewhere.
Yes, I think good cases can be made for utilizing the Abrams in either more defensive or more offensive roles. If these are brand new equipment, or in top condition, I'd say the offensive role gains advantage. Subterfuge has an important role to play in warfare, but at a certain point you need to lay down your cards and go into battle. I'd love to see some of these Abrams in action, pushing the Russians east. That is what they were built for really.