In your opinion it would not be better to omit the presence of the groove in all the tiles and indicate only the possible lack.
I know that it is contrary to the principle of expressing what is there and not what is missing, but in this case it seems to me that we would have more advantages than anything else:
in alphabetical order the first part of a tile family would be the neutral version (as is now the case for 1x3 tiles, 1x6 tiles and 1x8 tiles, but not for 1x2 tiles, 1x4 tiles and 2x2 tiles)
the descriptions would be shorter and more homogeneous (already now, most of the 1x4 and 2x2 patterned tiles do not give indications of the presence or absence of the groove)
the new parts are already with the groove, only very first versions were devoid of it (and there are many more patterned or stickered parts based on the grooved versions than on the others).
I know that it is contrary to the principle of expressing what is there and not what is missing, but in this case it seems to me that we would have more advantages than anything else:
in alphabetical order the first part of a tile family would be the neutral version (as is now the case for 1x3 tiles, 1x6 tiles and 1x8 tiles, but not for 1x2 tiles, 1x4 tiles and 2x2 tiles)
the descriptions would be shorter and more homogeneous (already now, most of the 1x4 and 2x2 patterned tiles do not give indications of the presence or absence of the groove)
the new parts are already with the groove, only very first versions were devoid of it (and there are many more patterned or stickered parts based on the grooved versions than on the others).