Make sure you didn't confuse this:
1) Did the printer said "Add bleed if you have elements going to the edges"
2) did he said "Add bleed and make your print-ready at the size of the bleed".
For #1, you do not add bleed or trim marks. For #2, you do add bleed.
It's normal they will mention to add bleed on a printer requirement/specification sheet as a tip. As you said, if the print people didn't see your design, it's possibly just the protocol. If you don't need bleed, don't add it.
Be careful in adding bleed when you don't need it; some printers blindly shrink your layout to fit a non-bleed sheet OR will charge you for a bleed print even if you don't need it. Or worse, they'll print the trim marks and shrink your layout to fit the sheet... Horrible true story scenario that can happen especially with digital printing or online printers.
If possible simply ask the printer. Local printers usually prefer to not have trim marks and bleed when they're not necessary, especially when using digital prints. It's ok if you put them but make sure to mention it.
White is absence of color, and transparent too. So adding a background or not doesn't matter. What's important is really the dimension of your file.