Whatever BA EC is doing with this RFS is a total mess. Not only on short haul, but also long haul.

As an example, you want to book from Tokyo to London (off-peak)?
-BAEC on BA: 35.000 WT or 39.000 WTP + £25
-BAEC on JAL: 31.000 + £26 in economy or 62.000 Avios in premium economy + £26

Now, if you book the exactly same BA flight via IBPLUS in WT: 19.500 Avios + £25 or WTP 39.000 Avios + £25

Essentially, for being loyal to BAEC, you are being penalised by 15.500 Avios for flying BA (in economy).

With the whole RFS system, they've lost the plot.