Seems like just a nomenclature thing to me. Prefixes meta, ortho and pyro are being sometimes used when giving names of inorganic acids to indicate a ratio of hydrogen atoms to the central atom(s).

And so:

• meta means an acid with a minimal number of hydrogen atoms in relation to central atom (given its oxidations state), e.g. (HPO3)n is metaphosphoric(V) acid
• ortho is a prefix given to an acid which has emperical formula having a H2O more than related meta acid, e.g. H3PO4 is orthophosphoric(V) acid
• pyro denotes an acid formed by condensation of an ortho acid, so pyrophosphoric(V) acid is H4P2O7

In case of a compound from your question NaAlO2 can be treated formally as a salt of "HAlO2" acid - which would be of meta type. However, this a nomenclature thing so skipping this prefix can happen.

Seems like just a nomenclature thing to me. Prefixes meta, ortho and pyro are being sometimes used when giving names of inorganic acids to indicate a ratio of hydrogen atoms to the central atom(s).

And so:

• meta means an acid with a minimal number of hydrogen atoms in relation to central atom (given its oxidation state), e.g. $\ce{(HPO3)n}$ is metaphosphoric(V) acid
• ortho is a prefix given to an acid which has emperical formula having an H2O more than its meta acid counterpart, e.g. $\ce{H3PO4}$ is orthophosphoric(V) acid
• pyro denotes an acid formed by condensation of an ortho acid, so pyrophosphoric(V) acid is $\ce{H4P2O7}$

In case of a compound from your question $\ce{NaAlO2}$ can be treated formally as a salt of "$\ce{HAlO2}$" acid - which would be of meta type. However, this a nomenclature thing so this prefix may be skipped.