That is true, but you can typically RMA the item - wouldn't be returning it to a store anyhow most of the time. Most quality manufacturers have a pretty respectable warranty on those items.
Newegg will not accept the item for RMA either once the UPC symbol is removed from the carton - It even says so on their site !! ( That is one of the reasons they offer so many MIRs in the first place
RMA processing time may vary depending on the product and reason for the return but generally processing time is 2-5 business days once the RMA is received and meet all following criteria:
1. Return with RMA number clearly identified in shipping label or on package.
2. Return with all original equipment, components, manuals, cables, documents, packaging.
3. UPC code along with retail package.
4. No physical damage caused by customer or by carrier.
5. Item is NOT out of warranty when it is received.
Notice Line 3 above !! - and yes they will refuse the RMA if the UPC symbol has been removed so make sure you are not going to try to return it before trying to get that $5 - $10 rebate !!