It would not stretch my imagination much to find that HM had Angela Kelly run up two replica gowns (in for a penny in for a pound), or that HM brought the original dress out for this very special occasion.
I don't think the original dress is an option at all, it's too fragile. From the look of the photo, Lucas is wearing something else, so either they switched gowns for each christening, or only August wore it.
I don't think it says anything more about Eug other than she wanted her son to wear the family gown. TBF, it's not the original and not the one she wore
To me it looks like the replacement but the colour seems a bit yellow.... 🤔