There is absolutely no truth to it.
It has become routine to deny any aspects of the ancient Indian culture which seem embarassing from the current perspective by attributing malevolence or ignorance to the so-called "Western" scholars and translators while all that they have done is a meticulous work just as they did with Egyptian hieroglyphics or Sumerian cuneiforms whose records and languages are much more ancient than even the Rig Veda and Vedic Sanskrit but were never preserved like Sanskrit was.
Instead of addressing that here, let us directly and simply cite an ancient Tamil poem that records a satī by a widowed Pandyan queen. Poems like these, isnpite of their antiquity, are pretty transparent to even modern Tamils due to astonishingly unbroken continuity of the language.
Voluntary satī is attested easily in ancient Classical Tamil poems, specifically the anthology Puranānūru with the various 400 poems dated from 200 B.C- 150 A.D and in medieval epigrahy (inscriptions).
https://sangamtranslationsbyvaidehi.com/ettuthokai-purananuru-201-400/
Here the widowed queen is resolved to enter the funeral pyre of her husband in spite the attempts by wise elders.
What follows is excerpted from that site and is a translation by Vaidehi Herbert a native of Tuticorin,, Tamil Nadu.
Puranānūru 246, Queen Perunkōpendu, wife of Ollaiyūr Thantha Pāndiyan PoothaPāndiyan sang this after the death of her husband, Thinai: Pothuviyal, Thurai: Ānantha Paiyul
You noble men! You noble men! You don’t let me go, you don’t let me die,
you scheming noble men!
I am not a woman who desires to eat old rice with
water squeezed out and placed on leaves,
without fragrant ghee as pale as the seeds of a curved
cucumber striped like a squirrel and split open with a
sword, along with vēlai leaves cooked with tamarind,
and white sesame seed thuvaiyal.
I am not one who wants to sleep on a bed of gravel,
without a mat.
The funeral pyre of black twigs might be fearful to you.
It is not fearful to me
who has lost my broad-shouldered husband.
A pond with thick-petaled, blooming lotus blossoms
and a fire are both same to me!
Notes: This queen, the wife of Ollaiyūr Thantha Pāndiyan PoothaPāndiyan did not desire widowhood, even though she was requested by elders to rule the country. She came from an ancient clan and was politically astute. She decided that the funeral pyre was better than living as a widow. Her husband, Ollaiyūr Thantha Pāndiyan PoothaPāndiyan, wrote Puranānūru 71. This king acquired the name Ollaiyūr Thantha Poothapāndiyan since he got back the Pāndiyan town Ollaiyūr from the Chōlas who had seized it.
Meanings: பல் சான்றீரே – O you wise me, பல் சான்றீரே – O you wise men, செல்கெனச் சொல்லாது – not telling me to go, not letting me go, ஒழிகென விலக்கும் – not letting me die, பொல்லாச் சூழ்ச்சி – cunning and scheming, பல் சான்றீரே – O you wise men, அணில் – squirrel, வரி – stripes, கொடுங்காய் – curved vegetable, cucumber, வாள் – sword, knife, போழ்ந்து – split, இட்ட – placed, காழ் போல் – like the seeds, நல் விளர் – fine white, நறு நெய் – fragrant ghee, தீண்டாது – without touching, அடை இடை கிடந்த – placed on leaves, கை பிழி பிண்டம் – rice squeezed with the hand, வெள் எள் சாந்தொடு – with white sesame seed thuvaiyal, புளிப் பெய்து – poured tamarind, அட்ட – cooked, வேளை வெந்தை – boiled velai greens, Sida rhombifolia, Rhomb-leaved morning mallow, வல்சி ஆக – as food, பரல் பெய் பள்ளி – bed of pebbles, பாயின்று வதியும் – living without a sleeping mat, உயவல் – sad, பெண்டிரேம் அல்லேம் – I am not like those women, மாதோ – an asai, an expletive, பெருங்காட்டு பண்ணிய கருங்கோட்டு ஈமம் – funeral pyre with black sticks in the big forest, நுமக்கு அரிது ஆகுக – might be difficult for you, தில்ல – அசை, an expletive, எமக்கு – for me, எம் பெருந்தோள் கணவன் மாய்ந்தென – since my wide-shouldered husband died, அரும்பு அற வள் இதழ் அவிழ்ந்த தாமரை – fresh lotus flowers with open petals, நள் இரும் பொய்கையும் – water filled pond, தீயும் ஓரற்றே – and fire are same
