Yes, the Spell Sage's ability can be used to meet the prerequisites for magic item creation.
The Pathfinder SRD has the following to say about magic item creation requirements:
Requirements: ... A spell prerequisite may be provided by a character who has prepared the spell (or who knows the spell, in the case of a sorcerer or bard), or through the use of a spell completion or spell trigger magic item or a spell-like ability that produces the desired spell effect. For each day that passes in the creation process, the creator must expend one spell completion item or one charge from a spell trigger item if either of those objects is used to supply a prerequisite.
The Spell Sage is able to use their ability to cast any spell "as if it were a wizard spell he knew and had prepared", which meets the criteria that a spell requisite can be provided by a character who has prepared the spell. The ability to do so once per day means that so long as they don't use the ability to replicate a different spell on a crafting day, they can meet the prerequisite during the whole crafting process.
This has the obvious caveat that if crafting a particular item required more than one spell the Spell Sage didn't normally know, they would have to suffer the +5 DC penalty for not meeting the prerequisite or find some other way to access the other spell, since this ability can only help them meet one such requirement at a time (the simplest way of doing so would just be to get a capable ally who can cast the spell to assist in the crafting effort).
You could probably argue about the precise wording of things from a Rules-as-Written perspective, but the intention of the crafting rules seems to be that almost any way you can possibly cast the required spell can be used to meet the crafting prerequisite (apart from using magical items that only require command words and can therefore be used by anyone - the logic seems to be that methods of producing the spell which require personal ability or skill should count), even if the original wording could be construed in such a way to exclude other ways of being able to cast the spells which were introduced by later material and archetypes.