> Does this actually mean something specific?

Probably:

Trade matching algorithms (prorata, FIFO, TOP) and rules (capital requirements, market impact definitions) will align with the interests of the most profitable customers.

Citadel Securities, with their HFT-level returns of 50-100% per year will not venture into a losing business.

Note, CitSec is different from Citadel (hedge fund), and the hedge fund is also crazy with 40% annual return before fees (past 20 years) and 19% after fees to the outside passive investor.

How does this compare to HRT?

No. They have planted a seed and Trees don't grow overnight.

Enron 2.0