OK I think I have a good theory on why their site says it is .25 micron. If you look at it, it says it is .25 under the section that says, "Mobile AMD-K6® Processor Features". They probably just did a copy/paste job from a different page for the mobile K6. Actually, the whole description page just talks about the value of the K6 266 or 300 and doesn't ever mention the K6-III+, so I think my theory is correct.
If you buy from them, as I just did

, you can be certain that if it is in fact a K6-III+ it is .18 micron and runs at 2.0v and runs cool.