That is a key strength. It is a strength which depends upon the flexibility and responsiveness. In turn, they derive in part from its cyclic process. You can view action research as a family of processes for combined action and research. Change often requires flexibility and participation.
Research depends upon high quality data and accurate interpretations.
Often it's useful to be able to meet both these conditions. Action research is designed to allow you to do so. Nor am I arguing for this version of action research over different versions. Different methods of research or action research achieve different purposes. For example, sometimes you may wish to identify causal relationships between relatively limited numbers of variables.