More problems with bricks and UART from (OpenWrt U-Boot layout) since it is not specified that it should be installed only from the SNAPSHOT branch, and it is not necessary to install it on routers with 1.0.84 yet since it does not work in recovery mode even on test builds where the switch in the firmware works and here it is definitely UART in case of recovery.
And regarding your question. The author himself confirms, although not with certainty, that if you update the stock from 1.0.31 to 1.0.49 before flashing, there should be no problem.
Write this as a necessary step for flashing to OpenWrt.