That line simply follows the most Northern Bulgarian villages. I only have one sample from Causeni and they are within the range for the Central region.
https://i.imgur.com/47Vvyvv.png
Samples in Stefan Voda range from being similar to the above and Central region (Mol-66 and Mol-69) to very Southern (Mol-15 and Mol-64).
These are the most up-to-date regional averages btw.
https://i.imgur.com/cZesUUw.png

