So who is correct? Or do you mean only when doing two of the same type of square e.g. 2 spiritual squares? Bcoz I've been doing both a material and spiritual Venus square at the same time which seem's to be going fine.
Performing one material and one spiritual square simultaneously is fine, provided they are spaced out with a few hours with precise affirmations. I have done this, and it was successful.
However, performing two material squares simultaneously, or two spiritual squares simultaneously - one with a longer mantra and the other with a shorter version - causes an energetic clash, as it invokes the same energies redundantly. This is just my perspective though. I haven't personally tried it, so I can't say with a 100% absolute certainty. It might work if one is extremely precise with the affirmations and the required repetitions for both vibrations and affirmations. Again, I can't be entirely sure as I haven't tried it.
However, I do one shortly after the other, like a few minutes apart since I'm short on time - how bad is that? I don't personally feel any conflict, the energies feel slightly distinct to me (in terms of inner vs outer).
Ultimately, I think you should be the judge here. I'd say this could interfere with your results, as the energies might clash and cancel each other out. But, if your intuition tells you it's working fine, then it could actually be the case.
Let me provide you with an analogy though:
Think of each square as a process that requires a specific concentration of energy, which is determined by the number of repetitions (e.g., 4, 18, or 54) needed for that day. If you do the required 4 repetitions (Square A), but then quickly follow with 18 repetitions (Square B) within a few minutes, then the second concentration (Square B) can interfere and disrupt the first concentration (Square A). This happens because the energy from the first session (Square A) hasn't had time to settle or "mature" yet, which may cause both Square A and B to lose its effectiveness and cancel each other out, ultimately leading to failure.
Therefore, spacing the squares out by a few hours or more allows the energies to integrate properly, which gives each square time to settle and mature before starting or continuing another square on the same day.