After the demolition derby incident, Donnie wanted to forgive his father. Splinter just wanted to win... But he apologized and said he DID want to spend time with donatello...

Why did it feel like he was lying..?

Donnie sat in his lab craving praise. He mindlessly tinkered, having an odd want to go home even though he was home already. His tech made him important, right? So if he wasn't doing that, hes... Useless. He just wants the recognition of the thing that makes him important.