Yes, they will not extend Ruby perks to you if you have your EC non-elite Blue number on a reservation.

If you were Sapphire or Emerald in one program but traveled with a different airline's frequent flyer number of a lower tier on your record and boarding pass, you could get the lounge access benefit by showing your current appropriate OW tiered frequent flyer card-the lounge staff might argue but it is not in the rules that you must have the OW tier eligible frequent flyer number in your record. For seat selection the reservation system probably requires a valid Ruby frequent flyer number in order for the agent to offer preferred seating to a passenger-your EC blue number on the record would prevent an agent from offering seat selection reserved for higher tiers only.