Under Part FCL rules, after 3 years since a rating has lost its validity it effectively requires a full type rating course again to Renew.
No, it doesn't, and never has. The requirement of FCL.740 is that, prior to the proficiency check to renew the rating, the pilot must
"take refresher training at an ATO, where necessary to reach the level of proficiency to safely operate the relevant class or type of aircraft". (my emphasis). The associated AMC states that,
"The amount of refresher training needed should be determined on a case-by-case basis by the ATO". The widely discredited tables implying that a specific amount of training was required according to the time since the rating expired have been removed from the AMC and replaced by a list of factors that the ATO should take into account when determining if and how much refresher training will be required.
For the removal of doubt:
The decision as to whether and how much refresher training is required prior to taking the proficiency check for the renewal of an expired type rating is entirely that of the ATO. (or DTO in the case of single-engine helicopters certified with 5 seats or less).