How am I supposed to judge that? How are you? Closed source software released by an evil company can't be trusted, full stop. If you choose to offer it limited trust, that's on you and you should understand the limitations of that trust if that's what you plan on doing.

You might have better luck blocking it at the network level. The downside of that is, depending on what is being sent over the network and why, it may no longer work. If you have to punch holes in it for server access, for example, now you no longer have any guarantee that the server port will not start collecting and sending telemetry that way. You also have no guarantee any server you connect to isn't also gathering and sending telemetry if it has network access to that port.

This is a slippery slope into a bottomless pit. Either cling to the side of it at your own peril, or give up and leap into the void. If you accept them getting some telemetry on you and you're happy just sandboxing it as much as you can, reducing the potential value of the telemetry as much a you can, and making it as difficult for them as possible, that's one thing. Go ahead and mod it with mods like this, put whatever limits you want on it, and hope they hold up over the long term against an evil corporation with billions of dollars to burn should they feel like it. You're counting on the fact that they won't feel like it, and that's probably fine.

Just understand what you're up against. There's no silver bullet for killing this monster. If you don't want any telemetry, that's what open source and trustworthy privacy-respecting maintainers are for. Minecraft has neither. If you're going to make a deal with the devil, you can do your best to make sure it's a good deal, but they're probably not going to follow it anyway.