Fernando, thank you for your patience in explaining this dilemma in such detail. Semantics indeed play an important part in all of this, and it is amazing to see the literal translation of 'taco' from Spanish =plug.
Naturally as someone who grew up in California with Mexican people, and living now in Texas, the word 'taco' instantly means the fried folded over tortilla with meat and cheese.......a food favorite
Apparently the word itself has numerous meanings in various contexts.
I am adding the pages from Roger Evans' book, and the first two pages of the 'plug bayonets chapter'. It seems that there are of course differences between the peasant knives which in certain degree recall plug bayonet form, but the 'spindle form' as shown by Udo, on p.158 it is noted "..there is no evidence that such knives were ever intended for use as plug bayonets".
This would be in accord with your observation that the Albacete daggers have' nothing to do with plug bayonets'.
However, on this page, Evans notes that TRUE PLUG BAYONETS were made in quantity for hunters by the cutlery trade in Albacete. Production likely began in the 18th century, but peaked in the 1860s and 70s.
It is unclear why these were termed plug bayonets if they were actually daggers, though the spindle grip type obviously could not be used in a gun barrel as Udo has noted. While the Spanish held to their smooth bore miguelet lock guns well through the 19th century, whether they actually used the plug bayonets in original form inserted in the barrel seems unlikely.