Prior to charging a lead acid battery, it is most important that:

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Charging a lead-acid battery relies on ions moving between the plates through the surrounding electrolyte. The electrolyte must be in contact with the active material on both the positive and negative plates so the chemical reactions can occur across the entire plate surface. If the plates aren’t submerged, there isn’t a continuous electrolyte path to support those reactions, so the charging current can’t flow properly and charging won’t proceed effectively. Exposed plates can also dry out or become damaged, leading to reduced capacity or failure.

Keeping the plates submerged ensures a proper electrical path and protects the plate surfaces during charging. While clean terminals help ensure a good electrical connection and the correct electrolyte composition matters, they don’t substitute for having the plates fully in contact with the electrolyte.