Early-type stars in some eclipsing binary systems have such small radii (and low luminosity) that only models near the zero-age-main-sequence with a heavy element abundance less than, or a hydrogen larger than, the solar value become in agreement. This result is contrary to what we expect from the current understanding of the theory of stellar evolution. As an alternative point of view, we construct differentially rotating models of such stars in some eclipsing binaries. Theoretical apsidal advance rate from these models are also in good agreement with observed rate. The rotational properties of stellar interiors vary from system to system and may be the key point for understanding chemical peculiarities and the magnetic nature of early-type stars. For further improvements in understanding the distribution of angular momentum within the stars, 3-dimensional models considering magnetohydrodynamic processes are indispensable.