Debug PlotLayout bug?

In[]:=
Clear["Global`*"];
In[]:=
StreamPlot[{{-1.5x,-y},{-1x,-y}},{x,-3,3},{y,-3,3},StreamPoints30,PlotLayout->"Row"]
Out[]=
StreamPlot[{{-1.5x,-y},{-1x,-y},{-0.5x,-y}},{x,-3,3},{y,-3,3},StreamPoints30,PlotLayout->"Row"]​​(*doesnotexecute!justgetasmall"beep"(andnomessage!)*)
The following does (but I’d prefer the style of PlotLayout):
In[]:=
graphs=Table[StreamPlot[{ax,-y},{x,-3,3},{y,-3,3},StreamPoints30],{a,{-1.5,-1,-0.5,0,0.5}}];​​g=GraphicsGrid[{graphs}]
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