In contrast the OrganicMaps folks with their home-grown data format efficiently share map data and make use of succinct data structures which is one reason their offline maps so small and efficient.

This is IMHO an unfair comparision, as the use case is different. A vector tile should be self-contained. A client app might only download a single tile and render it; without loading other tiles containing that information.

Organic Maps downloads all data of a country/region upfront, so it does know it can get the roadname at an adjacent tile if needed and thus can compress more.

@Strubbl: thanks for letting me know! I didn’t realise the diary entry had come through, as the account got locked due to the spam filter.