It is hard for a simple small consumer to be sure, but there are clues:
Violet leaf absolute is not made in India, Rose de Mai is a French specialty (made from French roses) and can therefor never come from Inda either.
India is well known for its fakes ande adulterated naturals. They can however still smell very good, there are realy good perfumers in India that make great substitutes. When you use it for fragrances and don't care much if they are the real thing you could try them, but I recommend to purchase quality. Problem is that this adulteration is not only done with products that do usualy not origin in India, but with typical Indian products too. It took me two years to get new davana oil that was accepted one of my suppliers, the others were found to be adulterated.
You probably noticed that all prices of these absolutes are about the same, that is unlikely, you would expect them to mirror the market. Mimosa should be cheaper (about 800-1000 GBP / kg), (french) violet leaf be more expensive (about 5000-6000 GBP / kg). Regarding the last, 5 ml violet leaf absolute, when sold at the common kg price would cost 25-30 GBP, that is excluding VAT, cost for the shop owner etc.. I must however be very carefull with this, for there is cheap violet absolute available from Egypt, and, though Egypt has an alike name as India, the Egypt absolute may be pure and reasonable available for 20 GBP at 5 ml.
Natural fragrances have some very good and some very bad aspects. On the good side: lots of them smell great. I don't know any perfumer who does not love a lot of naturals and in my top 10 of fragrance materials (that changes every day) are always a lot naturals. On the bad side: they smell different every year, so your perfume will smell different every year, unless you reformulate your perfume every batch. Another, more commom solution is to adjust the quality of the essential oil or absolute by adding suitable synthetics (or other naturals) to it, which is common practice. Another problem: you can't make more in case you need more. For instance when you have a fragrance that asks for cistus oil, well there is not made more than a few hundreds kg each year, for that is the usual demand of the market. Assume you are a big fragrance house, have a new fragrance with 1% cistus oil and it happens to be a great seller: you cannot purchase more cistus oil, because there is no more made, you have to wait for the new harvest, or... you purchase the strechted oil that is adulterated.
Let's assume you are an aromatherapist and want to have a longer lasting orange oil and a cheaper geranium oil. Well, orange oil contains a lot of limonene, limonene is prone to oxidation, so the orange oil has a short life, unless you replace it with another substance of course. Geranium oil can be much cheaper in case you stretch it.
And that is probably the bottom line: small businesses and private persons don't have the knowledge or means to check most quality aspects of an oil or absolute. The products are usualy not protected by any law. What we can compare is price and fragrance. When you can purchase 5 ml violet leaf absolute for a low price, and it smells good, why bother to even think of the posibility it is real.