Yes, their plot near West Slavs was based only on general R-M458 frequency, but R-M458 is in low frequency in Slovenia, they are predominantly R-M558. In Bulgaria, contrary to other South Slavs who are predominantly R-M558, R-M458 frequency is high (11% with at least 50% share of R1a), and similarly is in North Macedonia (7%, cca. 45%). So can be expected to find local drifts in Bulgaria and North Macedonia like in those Mijaks. Autosomally most probably would not make any difference, North Macedonian Slavs plot too much south from the southernmost Southwestern Slavs (Serbs and Montenegrins). They are around Bulgarians (not Northwestern Bulgarians).
EBalkansR1aSubcladesMatches.png
See
article "...ethnic Macedonians from North Macedonia (14+19/204) from Purps et al. 2014 and Jankova et al. 2019 (23-27 Y-STR)". Nevgen predicts:
R1a Z282>M458>> L1029>FGC66331
R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> L1029> BY30715 / YP1703 / YP417
R1a Z282>M458>> A11460
R1a Z282>M458>> L1029> BY30715 / R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> L1029> BY30715 / R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> A11460
R1a Z282>M458>> L1029>YP6048 / R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> L1029> BY30715
R1a Z282>M458>> L1029>YP593
R1a Z282>M458>> L1029>YP417
R1a Z282>M458>> A11460
R1a Z282>M458>> L1029> BY30715
R1a Z93>Z94> Z2123>Y934> Y7094
R1a Z282>Z280>> CTS3402>>YP295> YP335
R1a Z282>Z280> CTS1211>YP1034
R1a Z282> Y17491
R1a Z282>> CTS8816>>Y1392> FGC10360
R1a Z282>> CTS8816>>Y1392> BY32477 / R1a Z282>Z280> CTS1211>YP343>> YP371
R1a Z282>Z280> CTS1211>YP1034
R1a Z282>Z280>>Y35>YP4278
R1a Z282>Z280> CTS1211>YP1034
R1a Z282>Z280>> CTS3402>>YP582 / R1a Z93>Z94> L657>Y5 (possibly Y907(439=11,389i=13,570=19))
R1a Z282>Z280> CTS3402>Y2613
R1a Z282 > Z280 > S24902
R1a Z282>Z280>> CTS3402>>YP953
R1a Z93>Z94>S23592
R1a Z282>Z280> CTS1211>YP1034
R1a Z282>Z280> Z92>Y4459>> Y5570
R1a Z282>Z280> Z92>Y4459> YP5520
R1a Z93>Z94> BY32037