I do believe that it is indeed good amateur practice to do what is prudent to keep your equipment from being misused, yes.
But let's examine the legal aspects of the rules:
To quote the section in question:
§97.103 Station licensee responsibilities.
(a) The station licensee is responsible for the proper operation of the station in accordance with the FCC Rules. When the control operator is a different amateur operator than the station licensee, both persons are equally responsible for proper operation of the station.
The only issue mentioned is "operation" of the station.
Back up a but and you find this:
Subpart B—Station Operation Standards
§97.101 General standards.
(a) In all respects not specifically covered by FCC Rules each amateur station must be operated in accordance with good engineering and good amateur practice.
(b) Each station licensee and each control operator must cooperate in selecting transmitting channels and in making the most effective use of the amateur service frequencies. No frequency will be assigned for the exclusive use of any station.
(c) At all times and on all frequencies, each control operator must give priority to stations providing emergency communications, except to stations transmitting communications for training drills and tests in RACES.
(d) No amateur operator shall willfully or maliciously interfere with or cause interference to any radio communication or signal.
It is very clear that the rules are very specifically addressing the operation of stations.
There is no rule guidance regarding idle equipment since it cannot violate these guidelines.
It is very clear that operation of equipment requires certain conditions be met, as per:
§97.7 Control operator required.
When transmitting, each amateur station must have a control operator. The control operator must be a person:
(a) For whom an amateur operator/primary station license grant appears on the ULS consolidated licensee database, or
(b) Who is authorized for alien reciprocal operation by §97.107 of this part.
[63 FR 68978, Dec. 14, 1998]
§97.9 Operator license grant.
(a) The classes of amateur operator license grants are: Novice, Technician, General, Advanced, and Amateur Extra. The person named in the operator license grant is authorized to be the control operator of an amateur station with the privileges authorized to the operator class specified on the license grant.
(b) The person named in an operator license grant of Novice, Technician, General or Advanced Class, who has properly submitted to the administering VEs a FCC Form 605 document requesting examination for an operator license grant of a higher class, and who holds a CSCE indicating that the person has completed the necessary examinations within the previous 365 days, is authorized to exercise the rights and privileges of the higher operator class until final disposition of the application or until 365 days following the passing of the examination, whichever comes first.
[75 FR 78169, Dec. 15, 2010]
Therefore, any uauthorized operation violates the rules, and the violator is the person who initiates such unauthorized emissions.
So, to answer your question: "Do I actually need to lock up my station?" - the answer is based on your opinion of whether you feel a responsibility to prevent others from utilizing your equipment to break the law, and whether or not it requires that specific action.