Hola,
I think you do not have to worry about this. Usually, this soldermask spreading is used because at the PCB production there can be small missalignment placement of the solder mask, and if the soldermask have the exact form and dimension as the component pad, an overlap between these two will occur. Adding a small spreading in the soldermask will avoid this effect. However, this aspect is a concern only in high precision PCBs with very fine pitch pads. If you have relatively big components like 1206 and SO packages, then all is ok.
/pisoiu