A very interesting tactic, to be sure. It ignores a huge psychological factor, IMO.

Russian soldiers were tasked with invading another country. There is decent evidence that many conscripts were unaware of what they were being ordered to do. There is a lot of shared family ties between the countries. It is not surprising that a not insignificant number of those Russian soldiers vehemently disagreed with the invasion and switched sides to stop the invasion. Thus the Russian Legion was born.

It would be a HUGE psychological step for those same soldiers to go beyond fighting the invaders to actually invading their own country and killing their countrymen in their home countries.

The progression is straightforwad to my mind. It is easy to be a conscientious objector to the invasion. It is more difficult to desert your post in the middle of a foriegn invasion. It is even more difficult to fight against your countrymen in a foreign country. It would be supremely difficult emotionally and psychologically to take up the arms of foreign country and invade your own country, killing your own countrymen and destroying your own country.

On top of the psychological factors are the risk. These soldiers would understand explicitly that they would be dealt with as terrorists by the Russians. No quarter. The Geneva convention does not apply to them.

If some US soldiers in 2004 took the side of the Iraqis, formed a group and started shooting up Washington DC or a Raytheon weapons factory they'd have been hunted as terrorists. The same would apply to the Russian Legion in Russia.