Regarding the two B-type stars of the HR 6819 system, a recent news item (2 March 2022), European Southern Observatory researchers find 'vampire' star sucking outer layers of companion star states,
The current mass of the "vampire" star is roughly four to five times that of the Sun.
The other star's mass, originally perhaps five to six times the Sun's mass, now may be less than one solar mass.
If the mass of the so called "vampire" star is now roughly four to five times that of the Sun and the mass of its companion star now may be less than one solar mass whereas beforehand it was possibly five to six times the Sun's mass it would suggest that initially the mass ratio of the two stars was the opposite of what is currently is.
How does a smaller mass star predate a larger mass star, one would assume the initial gravitational situation would favor the larger mass star?