tfoot between thead and tbody for summary

When insuring W3C validation on a website lately, I saw that the tfoot tag must come before the tbody tag.  From the W3C spec: “TFOOT must appear before TBODY within a TABLE definition so that user agents can render the foot before receiving all of the (potentially numerous) rows of data.”  That makes sense but it’s benefit just clicked today.  The foot should function as the summary of the table data and thus let the user agent decide if it cares about the body.  Screen readers make obvious benefit of this.  I can see how search enignes would appreciate useful tfoot summaries as well as mobile applications.