Whalesong used the built-in bytecode compiler and compiled the bytecode to JavaScript. Reusing the bytecode compiler is in principle a good idea - but each time the bytecodes are changed, Whalesong needs to be updated.
And after the move to Chez Scheme as backend, the bytecode compiler is no longer a part of the main compilation path.
Is Racket bytecode different?
Racket is not [1]. It's just the internal representation that the compiler uses. Sort of like marshalling in Python.
[0] https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-6.ht...
[1] https://docs.racket-lang.org/raco/API_for_Making_Bytecode.ht...
Changes to the bytecode representation were indeed rare also in Racket.
The Whalesong project was written as part of a dissertation - and when people graduate and get jobs, projects are often abandoned.