I have seen that happen and sign up bonuses will always get abused if they are not strict, they usually ask for KYC to check if the player is not abusing the bonus, so if you do not agree with KYC better ignore casinos that offer sign up bonus, in the past, there are scam casinos that offer huge signup bonuses and they will make you win but before you can cash it out they will ask you to deposit so they can confirm with your address, once you deposit they will ban your account, I almost fall to this.
you are lucky not to fall into their trap. nowadays with the intense level of competition between many gambling sites, they make registration bonuses in the hope that it will attract a lot of new people but behind it all there are fraudulent sites that provide such bonuses just to deceive new users. the signup bonus is great but don't get caught up in it easily.
For people who are used to doing this, it is quite normal, but for those who are not used to it, including myself, I will not do this with a bonus that is not too big there.