When the advanced kernel configuration is chosen, and the user selects a configuration, it is not run as expected. Selecting menuconfig results in the scripts not running any configurator (causes an error on an initial build, as no .config exists) and selecting xconfig causes menuconfig to run.
The bug report explanations aren't detailed enough to fully understand the issue, but it's quite likely that it has been fixed by the merge of the linux-cleanup work, which has completely rewritten the Linux kernel support in BR. Therefore, I'll mark this bug as fixed. If the new linux-cleanup work still has a similar issue, feel free to reopen it.