The only thing that the compat level does is make certain query constructs behave as they did in the lower version. This does not mean that new functionality is disabled, only that functionality that has changed behaves the old way and not the new and that things which are not permitted in the new version still work in the lower compat mode (like *= only works with compat mode 80)

New functionality will work 90% of the time in the lower compat mode. This is intentional and by design.