No, after the death of Alexandre, the Argyraspides are simply the veteran hypaspists of Alexandre renamed in -327 for their bravery. They are hypaspists with silver shields only. It's only with the Seleucids that the name "Argyraspides" are re-used for the phalangits descendant of Macedonians.
The Argyraspides of Alexandre are different than the Seleucid Argyraspides who appear for the first time at the battle of Raphia (-217).

I simply wish to understand why the hypaspists are imagined armed with a short lance.


Note: the Argyraspides of Alexandre are a title "non-hereditary", the new hypaspists keeps the name hypaspists. During the battle of Gabiene, the Argyraspides are old from 70 to 80 years.