Random values do not guarantee fairness (given that it is proved to be totally random), you can not just use a random value generator on internet and just assume they are 100% or even 80% fair and that is because you don't know how they come up with the values and there's nothing transparent like blockchain to back it up, that's the whole idea behind gambling websites that use provably fair system and seed numbers that are being hashed and sent out to the players and even if players want they can add their own seed number to make sure that the gambling website is not tampering with the results, that way there is significantly less chance(still not zero) of any wrongdoing on the website part.
And worse, it is almost impossible to prove that these rngs are working as they should at most casinos and certainly for sure on Telegram. At least with provably fair dice most places show the code and it is clear how it works but for rngs,,, you can only trust audits you cannot see the code on your own with it all being closed source.