Since the photographer's readers are tap-to-read (unlike the long-distance on-ride auto-linking system), and they're attached to the photographer's equipment, you'd have to get *really* close to the reader for your card or Band to be read. (Plus, I think the photographer may have to actually press a button to start the linking process)
If you previously got someone else's photographer-taken photos added to your account, it's possible that the guests whose photos were taken immediately before yours were not scanned to their Band/card and were still in the "buffer" on the photographer's equipment. When the photographer then scans your Band/card after taking your photos, all photos in the "buffer" are then linked to what was just scanned. Thus it would link your photos plus the previous still-unlinked photos in the buffer. It has nothing to do with standing too close.
This goes against everything I understand in how the MDE and MagicBand system operates.
All Bands (whether received free as part of a hotel reservation, or those purchased separately) are simply "pointers" to your MDE profile. Whenever the Band is read, the system uses the Band's serial number to look up your account and add the photos to the account it's linked to. Now it's possible if a Band isn't properly linked to a MDE account for it to not link the photos correctly, but if the Band shows up under "My Bands and Cards" in your MDE profile, then any photo linked to said Band should also appear.
-Rob