To summarize what the report says, it seems like most of the Eastern Military District (EMD) is at the southern/eastern frontlines with elements from the southern md as well. This translates as a vacuum of support from rear lines that could be essential in the event that part of the line needs to do a tactical retreat.

The report also makes the common confirmation that Russia's lines of defense are extensive and well prepared, and it will take a huge effort to pierce them, however if Ukraine is successful in doing so, lack of reinforcements could possibly make the line crumble.