  Large hadronic elliptic flow $v_2$ is considered as an evidence for the
existence of a strongly-coupled QGP fluid in high-energy heavy-ion collisions.
On the other hand, direct photon $v_2$ has recently been found to be much
larger than hydrodynamic estimations, which is recognized as "photon $v_2$
puzzle". In this study, I discuss the implication of late production of quarks
in an initially gluon-rich medium because photons are coupled to quarks.
Numerical analyses imply that thermal photon $v_2$ can be visibly enhanced.
This indicates that interplay of equilibration processes and collective
expansion would be important.
