Separate digital service from GDS
So that would be like every other department's digital service, then.
GDS is the Cabinet Office's digital service. It defined the approach (taking best research, design and development practices from the private sector); it also helped all the departments and agencies to consolidate their content from hundreds of separate sites onto a single GOV.UK site.
Other departments and agencies, like DWP, Dept of Health, HMRC. Home Office, Ministry of Justice, DVLA and many others each have their own separate digital services. While they follow the lead and template set by GDS, they are separate entities, with their own respective budgets and operating in their own way.
Parliament is doing exactly the same thing. So this is perfectly normal - whether it's a good or a bad thing entirely depends on how well Parliament do their research, design and implementation.