I’ve had two Absolute Black Cinch ovals which were claimed to fix the chain line for non Boost bikes back to 49mm. They don’t. On one bike I could move BB spacers around but on the other I wasn’t able to.
I found out when I bought a OneUp Cinch oval that had 6mm of offset and did indeed fix the chain line to 49mm.
Then when I put an original Race Face Cinch 51mm DM ring next to the OneUp and the Absolute Black it was really clear that the OneUp is much thicker and offset more.
If your bike works fine with 51mm chain line… go ahead. The AB rings are fine.
If your bike doesn’t work so well with 51mm then buy the OneUp “standard” Cinch rings with 6mm offset on them.
This isn’t so much an issue with 10 speed cassettes but it’s a real issue on 11 speed Shimano or the chain drops when you backpedal in 1st.