This is a house rule intended to make the Identify spell a little more limited and define what the spell provides in terms of information.
The rules around spellcasting components in the Player’s Handbook state the following:
If a spell states that a material component is consumed by the spell, the caster must provide this component for each casting of the spell.
The identify spell has a material component requirement of an owl feather as well as a pearl worth at least 100 gold pieces. However, it does not explicitly state that the pearl is consumed, meaning that the same pearl can be used again and again.
The Identify spell requires the pearl to be crushed, dissolved in liquid, the liquid needs to be stirred with the owl feather, and the liquid needs to be consumed. This means that the pearl is consumed during casting.
According to the Player’s Handbook, any component that has an explicit value, or is consumed, cannot be replaced by a spellcasting focus. In this case, only the owl feather can be replaced by a spellcasting focus, which will need to be on hand while the crushed pearl is stirred by other means.
The effect of the spell is that it gives insight into the item’s abilities, but the history of the item will still be unclear. While certain bits of information about the history of the item might become clear through the Identify spell, a Legend Lore spell is required to learn the precise history of the item. The less frivolous and more powerful the item, the more likely there are important details to its history that will impact the character using the item.
A number of items up to the spellcaster’s proficiency modifier can be identified with a single casting of the spell.