We actually do log a warning at runtime in case ParameterMessageInterpolator is used and an EL term is discovered. So the warning in the constructor seems not really needed.

Although I'd actually argue that in your case – Spring choosing an interpolator as per the environment, i.e. it's not an explicit choice by the application developer AFAIU – the warning makes kinda sense, so to give an early warning up front, before messages go uninterpolated. So are you sure you really would like to have it removed?

Taking a step back, we could log all the configured options (interpolator, but also traversable resolver etc.) on DEBUG level, aiding the user with understanding the effective settings, esp. when not in control of the bootstrapped validator (factory) themselves.