So, is the concern the extension piece, or that the bars offer forearm support? IMO, that plastic piece on the front doesn't look sturdy enough to grab hold of and steer if that's what you have in mind.
Here's what the UCI has to say about it:
1.3.022 Provided that they comply with the criteria mentioned in this article, handlebars known as “delta”, “cowhorn”, “triathlete”, which have short handlebar extensions may be used exclusively in the following events:
Individual and Team Pursuit
Kilometre / 500 m Time Trial
A forearm or elbow-rest shall be permitted. In other races, the handlebar type shall be "classic" and no part of the handlebar may protrude forward of a vertical line passing through the front wheel axle (modification came into force on 1st January 1998)