  The recent discovery of a galaxy at z=7.3 with undetected optical emission
lines and a blue UV to optical continuum ratio in JWST spectroscopy is
surprising and needs to be explained physically. Here, we explore two
possibilities that could cause such a seemingly quiescent ~5e8 $\rm M_\odot$
galaxy in the early Universe: (i) stochastic variations in the star formation
history (SFH) and (ii) the effect of spatially varying dust attenuation on the
measured line and continuum emission properties. Both scenarios can play at the
same time to amplify the effect. A stochastic star formation model (similar to
realistic SFHs from hydrodynamical simulations of similar-mass galaxies) can
create such observed properties if star formation is fast-varying with a
correlation time of <150 Myrs given a reasonable burst amplitude of ~0.6 dex.
The total time spent in this state is less than 20 Myrs and the likelihood of
such a state to occur over 500 Myrs at z=7 is ~50% (consistent with current
observations). On the other hand, we show that a spectrum with blue UV
continuum and lack of emission lines can be reproduced by a blue+red composite
spectrum. The UV continuum is emitted from dust-free density bounded HII
regions (blue component), while the red component is a dust-obscured starburst
with weakened emission lines due to strong differential dust attenuation
between stellar and nebular emission. Future resolving far-infrared
observations with ALMA will shed light on the latter scenario.
