So you would like Dimensions which only respects List head? Good question. -- Kuba

From the documentation:

The "array" is considered full only when it has the same head as at the top:

 

Dimensions[f[g[x, y], g[a, b], g[s, t]]]
{3}

So I believe, this could be achieved like so:

listDimensions[arg_] := Rest@Dimensions[{arg}]
listDimensions[a.b]
listDimensions[aa.bb]

{}
{}

So you would like Dimensions which only respects List head? Good question. -- Kuba

From the documentation:

The "array" is considered full only when it has the same head as at the top:

Dimensions[f[g[x, y], g[a, b], g[s, t]]]
{3}

So I believe, this could be achieved like so:

listDimensions[arg_] := Rest@Dimensions[{arg}]
listDimensions[a.b]
listDimensions[aa.bb]

{}
{}

So you would like Dimensions which only respects List head? Good question. -- Kuba

From the documentation:

The "array" is considered full only when it has the same head as at the top:

Dimensions[f[g[x, y], g[a, b], g[s, t]]]
{3}

So I believe, this could be achieved like so:

listDimensions[arg_] := Rest@Dimensions[{arg}]
listDimensions[a.b]
listDimensions[aa.bb]

{}
{}

So you would like Dimensions which only respects List head? Good question. -- Kuba

From the documentation:

The "array" is considered full only when it has the same head as at the top:

Dimensions[f[g[x, y], g[a, b], g[s, t]]]
{3}

So I believe, this could be achieved like so:

listDimensions[arg_] := Rest@Dimensions[{arg}]
listDimensions[a.b]
listDimensions[aa.bb]

{}
{}