Yes, but now you're comparing a T-grain film to a conventional film - isn't it also true that Pan-F is sharper than FP4+ or that Delta 100 is sharper that Delta 400?
Also, when Ilford says sharper, what do they mean? better acutance, higher resolution, or both?
Well, no, not strictly T-grain: the difference between T-grain and Delta (epitaxial growth) isn't just marketing speak. It's also true that the distinction between monosize controlled-growth crystals (Delta/T-Grain) and conventional cubic crystals with the current generation of both 'traditional' and 'new technology' films is a lot less than it used to be.
What is more, not only is T-grain more sensitive to overexposure and overdevelopment than Delta, but the 'quality crash' that you get with either or both mistreatments is worse: by this I mean the point at which sharpness is actually worse than with traditional films, as as a result of mistreatment.
With this in mind, the sharpness is indeed higher with the slower films in each emulsion type.
Like most manufacturers, Ilford define sharpness in terms of MTF.