For the snap, this is because data_dir in distro_info is hardcoded to /usr/share/distro_info/ whichi corresponds to the version included in core18 not the version that ships with the snap itself.
Version 20200427 (1754) of core18 contains the right data file with information about groovy.
distro-info could be updated to allow an override of data_dir instead of using a hard coded path.
Meanwhile you can either wait until latest core18 is released to stable or upgrade core18 to latest/candidate.
For the snap, this is because data_dir in distro_info is hardcoded to /usr/share/ distro_ info/ whichi corresponds to the version included in core18 not the version that ships with the snap itself.
Version 20200427 (1754) of core18 contains the right data file with information about groovy.
distro-info could be updated to allow an override of data_dir instead of using a hard coded path.
Meanwhile you can either wait until latest core18 is released to stable or upgrade core18 to latest/candidate.