Agree - I do not see how useful this is - as BF is many times cheaper than full Y.
RT Examples:
EWR-LHR in BF = $2404 + 205 = $2609 (BF R Class comes up) Jan 21 return 28
EWR-LHR in Y = $3568 + 145 = $3713 (Coach Y Class) Jan 21 return 28
Full Y needs miles to upgrade as well.