This is freedom of contract
The company sells one product to everyone, System A.
The company also sells Tech B to only its pre-existing customers.
That is not bundling under the general ideas of antitrust law or Product Bundling under competition laws, as you don't have any secondary items, and two wholly distinct sales.
The company offers its products separately. The best equivalent would be a line in a restaurant menu that lists "extra patty for your burger" that is only sold as an option for your Hamburger but not alone. Just rephrase the offer to "Tech B for our customers of System A".
There might even be reasons why Tech B is not offered on its own and can't be bought by non-customers of System A. The most simple would be that Tech B is pre-installed with System A - but it is not bundling because you already need to own System A to buy Tech B and Tech B is not offered as machine that can run system A but machine set up to run System A - which is not a bundle but a different product, just like gluten-free cake is to normal cake.
Nothing forbids negotiating
That doesn't mean that legally you can't get the Tech B: you just would need to negotiate with them for it, outside of the normally offered items.
