So again, a ton of convoluted speculation following, but if SAPOL told the truth, if one and only one of the Oak Park Station grandparents is "the suspect," and if JM and SM know which one of them it is, while their lawyering up at the same time looks pretty similar from the outside, their lawyers have significantly different jobs to do to try to serve their respective clients' best interests. Particularly IF this actually IS a major crime and IF 'the suspect' is guilty of it, meanwhile the other may or may not have acted as an accessory after the fact, however willingly or unwillingly, knowingly or unknowingly. If both JM and SM are smart, they've each told their respective lawyers what they know, what they've told police, what they haven't told police, and any relevant details (including family dynamics that could be influencing the situation), everything (seriously, do not keep secrets from your lawyer).
It's likely in the best interest of 'the suspect,' particularly if guilty, to not say anything. It would also likely be in the best interest of 'the suspect' for the other grandparent, not the suspect, to also not say anything, also not cooperate, help present a unified front of stonewalling and to make it harder (or impossible), for SAPOL to differentiate between which parts each may have played in this, cast doubt, give them nothing to look into or work with so they can't gather enough to press charges, and create plausible deniability if charges are brought against 'the suspect' for the death of Gus Lamont and this gets taken to court.
Meanwhile it would likely be in the best interest of the grandparent who isn't the suspect, if not guilty, to draw a clear distinction, to create distance/differentiation and not get turned into a human shield/smokescreen for the suspect, and make it clear to SAPOL that they weren't responsible for this and are on the side of wanting justice for Gus. Including maybe to proactively demonstrate their innocence, be cooperative, and hopefully not get pulled any further into it. While personal loyalties to each other and other emotional considerations could muddy this for the Murrays, this would probably be the aim for their respective lawyers and so would shape the advice they'd give their clients to follow, even though, again, on the surface, almost certainly share a very similar 'don't speak to LE without me present.'
In this light, and IF JM is the suspect and IF SM is not, and IF SAPOL is on the right track with both this designation of major crime and who they believe committed it, and IF the dynamics in the home have been preventing SM from being able to safely cooperate fully with SAPOL...IMO, it would completely make sense for SM's lawyer to coordinate a time with SAPOL, likely when he could be present, when Shannon could walk them through what she knows while JM is conveniently out of the way for the time they need at Oak Park Station. IMO, that could be the actions of a competent defense lawyer representing the best interests of an innocent client who lives with the suspect for (and potentially perpetrator of) a violent crime, one whose own best interests are that she keep her mouth shut.
That's a lot of 'ifs' that would need to line up a certain way, but IMO it would fit cleanly within what just happened and also within the broader context of this case. MOO.
TLDR: It might not have been without a lawyer present. It could have even been partly organized with the lawyer, for above reasons.