There is no sRGB chunk, nor any ICC chunk.
If it is linear (not sRGB), which seems to be the case: then RGBA8888 has too little precision. (Will it be possible to export to eg RGBA at 16bpp?)
If it is non-linear (sRGB): how is alpha premultiplied?
To be correct, it should be:
f(R * a), f(G * a),f(B * a),aThat is, it should be multiplied by f(a) not by a. Where f takes linear value to sRGB. (Otherwise it would mix linear and non-linear color space and blending would be off).