No longer my area, but I am surprised that market manipulation can only be achieved by an act rather than an omission so that a failure to bid could not be prohibited. It seems to me the question is really why there was a failure to bid: was it to secure a dominant market position and, if that were the intention, was the failure likely to have the effect of fixing prices or creating other unfair trading conditions?
EU MAR, Article 12.2. The following behaviour shall, inter alia, be considered as market manipulation:
a. the conduct by a person, or persons acting in collaboration, to secure a dominant position over the supply of or demand for a financial instrument, related spot commodity contracts or auctioned products based on emission allowances which has, or is likely to have, the effect of fixing, directly or indirectly, purchase or sale prices or creates, or is likely to create, other unfair trading conditions;
[Clearly you should not rely on this back-of-the-envelope legal analysis for any purpose whatsoever.]