Firstly: unless you know what you’re doing (which from this perspective means that you’re comfortable reverse-engineering Javascript, using a packet sniffer or network debugger, etc.) you should try to avoid clicking these links or providing any data whatsoever. In short; if you wouldn’t be able to determine how the tracking was working, you probably shouldn’t play about with it. Supposing you’re right and they had connected the session to your phone number already, what you do by interacting with the form is show that your phone number is real and that the person who receives texts at it will, under some circumstances, click suspicious links. That in itself is valuable information for an attacker. Similarly, unless you know that the phone numbers you typed in weren’t actually submitted (that you were told they were “formatted incorrectly” doesn’t necessarily prove that they weren’t collected), you definitely shouldn’t provide real numbers, even ones of people you “don’t like”, because you’re establishing a connection between you and them that could potentially be exploited later. Also, it’s clearly unethical.

If you’d like to send me the link from the text you received I can take a look and try to tell you how the “tracking” works. I’ve come across a small number that do clearly do some tracking to link it back to your phone number, but those tend not to ask for a phone number at all from the form, or just show the phone number they sent the text to. Showing “formatted incorrectly” for any number but yours would be a bad idea from the scammers point of view because a legitimate redelivery site would probably accept a different number (e.g. if you wanted to provide your second mobile, your partner’s, your landline or whatever), thereby raising suspicion.

My guess would be that the scam site might be badly implemented, but personally: I wouldn’t start entering numbers of any kind into such a site in the first place unless I felt confident in being able to diagnose that, if it were the case. I’d suggest you take the same strategy and, when in doubt, don’t “play about” with these sites at all.