why does French voice thomas mispronounce "allé"

Question

The commands

say -v Thomas 'il y est allé.'
say -v Amelie 'il y est allé.'

reveal that currently, Thomas, a supposedly French voice, is incapable of pronouncing the extremely common French word "allé". Instead, he spells it out. This would be like an Englishman not recognizing "gone" and instead spelling it "G, O, N, E."

By contrast, Amelie, a Québécoise, i.e., French-Canadian, voice, says it properly. What is wrong with this Thomas voice and can this be repaired?

This is tagged "mojave" because I only recently became aware of this, since upgrading.

Note that Thomas is a French voice:

> say -v? | grep fr_
Amelie              fr_CA    # Bonjour, je m’appelle Amelie. Je suis une voix canadienne.
Thomas              fr_FR    # Bonjour, je m’appelle Thomas. Je suis une voix française.

which you can confirm by the mess he makes of

> say -v Thomas Hey there, man

So I see no reason that say would have to have my computer's language set to French. One of the benefits of all these voices is that you can get French read by a French speaker, German by a German speaker, Arabic by Arabic, etc.