3-4,6-3Enclosure/Query

Deprecated?  

According to Enclosure Josekis, (rather than a - see hanging connection to the second line as good shape) is bad shape.

Which it may well be; but there are a number of examples of this in recent pro games, when Black already has a stone at b or even c.

A standard ko  

For example with present, White may end up with this shape, an incomplete comb formation in the corner; which becomes ko after Black a. Much will depend on White's scope for causing trouble on the outside. Black at b becomes very thick.

See for example games Kato Masao-Kobayashi Koichi 1997-02-01 and Kudo Norio-Kobayashi Koichi 1998-12-10.

Charles Matthews