The Russians did stop within rage of Auschwitz-Birkenau for months, fully aware of what was happening there, allowing the Germans to continue their genocide.
That's not true either.
Operation Bagration had inflicted enormous casualties on the Germans but also on the Russians.
The offensive had moved the line west by hundreds of miles of scorched earth.
As they approached the Vistula the Soviets started encountering more Germans because the Germans
had set up strong defensive positions there.
You can't just keep advancing indefinitely. Modern armies need a lot of resupply, they can't just live off the land.
Von Manstein demonstrated this in the third battle of Kharkov in 1943 where he lured a rapidly advancing
Red Army into a trap when he saw that they were outrunning their supply lines.
The Soviets needed to sort out logistics, rest their exhausted troops and bring in and integrate fresh troops
to replace their casualties as well as replacing all the equipment they had lost.
The Vistula was a natural point to do that.
The goal of the next and final offensive would primarily be Berlin (Auschwitz wasn't even in that direction).
There is no evidence at all that Auschwitz formed any part of considerations the Soviets made one way or another,
it simply wasn't relevant to planning what they would do next.
The Soviets paused primarily for military reasons (they did (cynically possibly) pause very close to Warsaw but there were well over a hundred miles from Auschwitz).
In fact I don't know if there is evidence that the Soviets knew what Auschwitz was until they got there.