The test he took, with the Belgian juniors, where he climbed 15 seconds slower than 3 year older Lambrecht on Ballon d'Alsace was from 2017 (the year Lambrecht lost Tour de l'Avenir to Bernal with 69 seconds).
Here is an article from 2018, posted by 18-Valve. (pithy), where Bomans talks about that test "l'an dernier" (last year), meaning 2017. But you are correct and he must have done another test a year later as well. He
talks about it here in an article posted by DNP-old: 7W per kg, on the entire climb (23 minutes) how i understand it. All his Strava records seem to have been wiped though (at least i can't find any from either year).
Tenth of January, team presentation.