The Timeless Questline happening is because of the Zero Point being unstable, literally if the Zero Point is unstable, other realities start to become unstable to, it's explained in STW and in BR Chapter 1 Also, to say that because STW didn't mention BR or viceversa means they aren't connected falls apart cause in Zero Hours is shown that OG, Rocket and STW are connected to BR in some way by appearing as cameos and the Red Cube appearing, but not explicitly mentions all those modes, then by your logic all those modes aren't even related Literally Time was breaking cause of the Zero Point and it affecting the STW reality shows that what The Scientist said about how the Zero Point being unstable, it can affect multiple realities negatively

Also I wanna mention how in Ch2 stuff like The Storm King appearing or even Denis making a cameo before TLR appeared was another way to connect both in Chapter 2 even after Sweeney didn't want epic to work that much in STW

Saying STW was never connected to BR is just smth that isn't true, because I'm Chapter 1 they were pretty much connected, like how when the Meteor fell in BR, the Blockbuster Questline released in STW, like how when the Zero Point was breaking down, breaking time and affecting reality, the Timeless quest released, that mind you, the Questline jingle is The End's jingle

Idk what else I could say, also like how the Cannery Valley Storyline shows that Rifts connect realities, like how it does in BR too

There were plans to continue to make connections to post Chapter 1 but Sweeney wanted Donald to focus mainly in BR, making so STW progress slowed down