Hi,
Doing as you described is a no go.
3 operations just to restore the image, and the worst part is that the alpha is no longer there.
In photoshop I just open the file, right click, load the selection and do my job.
There has to be a solution. The information is alredy in the file.I do not need to restore it.
I really like Affinity, it can do everythig and it is cheaper....... wich counts a lot.
In architectural renders alpha channels saved in Tiff or exr files are a must have. Some files have more than one render with different alphas for different parts to compose.
Best Regards,
Fernando Blanco