That’s not how ERA, even heavy ERA works. It doesn’t deflect penetrator rounds down through the hull - and modern APFSDS sabot rounds don’t ricochet off much anyway.
You’re also forgetting that the T-90S has an active protection system that will destroy the TOW before it gets close enough to damage the tank... and no NATO main battle tank, until the crash program to mount the Israeli Trophy system on a few US Abrams tanks, has an APS. At all. Which is why the Turks are having their Ex-German-Army Leopard 2A4s and 2A5s ripped apart by Russian Konkurs missiles. Single Konkurs take out NATO standard tanks, where in the Chechen wars taking out a Russian APS-protected tank took at least six fired in a swarm attack to saturate the defense.
It’s Kontakt-5 ERA. Versus the US M829A3 and M829A4 rounds it is ineffective.
“However patents from Alliant Techsystems (ATK) show us a different possibility of the M829A3 design: instead of utilizing an elongated DU penetrator with conventional tip to defeat tanks fitted with heavy ERA by “brute force”, it is suggested to use a special tip assembly to overcome ERA. The tip is a solid steel construction with a length “greater than 100 mm”, while the main penetrator has a length of “about 630 mm, preferably greater than about 650 mm, and more preferably greater than about 670 mm”. Specifically the last value is interesting, because this is very close to the reported length of the penetrators used in the previous M829A1 and M829A2 APFSDS rounds. Furthermore the thickness of the rod was increased from 22 to 25 mm, which result in a 67% higher bending stiffness (and thus better performance against ERA).
Such a penetrator design has a big benefit against targets protected by heavy ERA, which is what the main target of the M829A3 development was. The solid steel tip will punch a hole into the ERA, but is designed with a special weakpoint at the connection to the main penetrator; it will break of instead of transfering the stress created by the interaction with the ERA-plates onto the main penetrator. While the M829A1 was unable to defeat the contemporary Soviet tanks with Kontakt-5 heavy ERA, the M829A2 was designed as “brute force” solution against Kontakt-5 armed Soviet tanks. The M829A3 was the “elegant way” to defeat better armored tanks with Kontakt-5 or the follow-up ERA.”
https://below-the-turret-ring.blogspot.com/2016/02/m829a3-apfsds-penetration-power-common.html