Boot LS Classpath notification mode is off at the beginning in Hybrid mode. Then it becomes on when Java LS is started in Standard mode a bit later. However at this time Boot LS may not be up since it is up when spring-boot is discovered on classpath and hence enablement of classpath listening goes blank :-
The result of this bug is troublesome as all features of Boot LS are not working because there are no boot projects discovered in the workspace.
The workaround is switch to Standard launch mode of the Java LS.

The solution on the spring-boot tools extension would be enable classapth listener when boot ls is started via the command (command executed via Java LS when spring-boot discovered on the classpath)