Is it?  older clients by definition does not know about "type", no?

Newer client, older remote server was the situation I was thinking
about

I am perfectly happy with the capability advertisement to say not
just "object-info", but also what attributes of objects you can be
queried, by the way.  If clients right now (i.e. without this
series) expect that the other side who advertises "object-info"
without "=<these>,<attributes>,<are>,<supported>" supports only
"size", for example, perhaps treat the bare "object-info" capability
just as a synonym of "object-info=size", or something?

This is a good idea! Thanks