In several of my books such as Yoga Meditation, I have written about the importance of having a good-quality meditation posture such as Padmasana, Siddhasana or similar. If you cannot sit comfortably chances are that discomfort will stop you from going deeper into spiritual insight. The key to most meditation postures is to be able to rotate the thighbones internally enough so that the knees are protected and the pelvis is sufficiently tilted anteriorly to keep the low-back lordotic, thus preventing low-back pain.
Yes myth… the myth is that iliopsoas is functionally one entity. Iliacus and psoas and two individual, unique and independent muscles that share the same insertion on our thigh bone. Their important origins are totally unrelated. Akin to partners sharing the same household they can work together to achieve certain outcomes and at the same time have unique qualities that they express totally independent of the other. As both are strong ‘characters’ with important roles to fulfill they sometimes run into trouble and hence the infamous reputation!