Yes, it's just a container for the exact same data that an OpenType font holds.
On the other hand, it's possible that in the course of deployment, various things may be dropped from the original font resource: not just subsetting (reducing the repertoire of supported characters), but in some cases also OpenType features (e.g. ligatures or contextual forms), and in some cases hinting is stripped.
If that is done, the webfont version may indeed appear differently than the original "desktop" font, depending on local font-rendering settings.
Mea culpa, I've done this once before. I work on a small 4k screen so I couldn't tell the difference, though others pointed it out and I fixed it. I was trying to eke out that last bit of performance.
On the other hand, it's possible that in the course of deployment, various things may be dropped from the original font resource: not just subsetting (reducing the repertoire of supported characters), but in some cases also OpenType features (e.g. ligatures or contextual forms), and in some cases hinting is stripped.
If that is done, the webfont version may indeed appear differently than the original "desktop" font, depending on local font-rendering settings.