thyristor latching and holding current confusion
The latching current is associated with turning on the thyristor, the holding current to turning off.  If the current through the load is not large enough the thyristor will not turin on correctly and will turn off as soon as the load is reduced.

The holding current is the current required to maintain conduction once it is established with 0 gate current.

Here is one site that gives a good description:

Description of latching vs holding current