If the tables are displaying the same number of columns, I would say it's a better experience to have a shared width of the columns; however, if you are displaying a different number of columns, probably not so much.
If the tables were not groupings of a similar nature - using the same column widths may actually be a negative experience, because people have a tendency to see patterns as being the "same".
Do they look at tables independent:
To find out the absolute answer - you would want to test your specific users. Having said that, it depends on how they are styled or chunked - to put it in a general terms.
If you have 5 tables vertically down the page - each with the same number of columns - with no more spacing than what you have in the mockup, your users will most likely group them together as being similar (which may be good or bad - it depends on if you want them to consider the data to be similar or not). If you have one table placed on one side of the page and another on the other, with a different number of rows and/or columns - then probably not.
For the wireframe you have - it is "bad". However, the users will probably see table one containing information from category 1 and table 2 containing information from category 2.
But, the rule of thumb still applies. Tables lined up in the same vertical space - with varying column widths - despite having the same number of columns, break "the grid" - and will most likely cause the user's brain to do a little hiccup; or, think it was unintentional.
I hope that helps clarify things.