IRS receives all your tax documents. That doesn't excuse you from supplying required documents with your tax return.
Yes mailing the consolidated 1099-B is redundant.
Many filers just don't bother to follow the rules.
If you have transaction detail to supply and you are mailing your return, attach it.
Form 8453 is just a cover sheet and is used only if you e-File and you have three business days after your return is ACCEPTED to mail the paper documents to IRS in Austin TX, which is not a regular filing place for form 1040.
