  The origin of extended main-sequence turn-offs (eMSTO) in star clusters
younger than 2 Gyr still challenges our current understanding of stellar
evolution. Exploiting data from Gaia Data Release 3 (DR3), we investigate
eMSTOs in a large sample of 32 Galactic open clusters younger than 2.4 Gyr. We
first validate Gaia rotational velocities from Radial Velocity Spectrometer
(RVS) spectra by comparing them with literature values and assessing their
correlation with magnetic activity measurements from LAMOST spectra. We detect
a general positive correlation between turn-off color and projected stellar
rotation, with slow-rotating stars predominantly found on the bluer side of the
turn-off. Comparing our observations with theoretical models, we find that the
eMSTO morphology is well-reproduced by a single population formed with a high
rotation rate, and observed with rotation axis inclination ranging between
0$^\circ$ (pole-on) and 90$^\circ$ (edge-on). This contrasts with observations
of Magellanic Clouds clusters, where a population of non-rotating stars appears
to be ubiquitous in clusters younger than 700 Myr. However, we note that our
interpretation, while successfully explaining the overall eMSTO morphology,
cannot fully explain the observed projected rotational velocities.
Additionally, two young clusters, NGC 3532 and NGC 2287, exhibit moderate
evidence of a split main sequence in color and rotation, suggesting a possible
small spread in the initial rotation rate. Finally, we advise caution in
determining the ages of young clusters from non-rotating isochrones, as
neglecting the effects of stellar rotation can impact the isochrone dating by
up to factors of 5-20%.
