grammar - Newspaper headlines + is it possible to use present perfect?

I've found these two sentences in newspaper headlines and there are two things I am not sure about:

1. Haas beats Wawrinka
   Tommy Haas claimed the biggest win of the season against Wawrinka. He beats #3 in the World 5-7/ 6-2/ 6-3 and reach the quarterfinal in Rome. On the Foto is Tommy with a icepack after the match. Now he has 1.45 hours rest before the doubles start.
   Source

Do I understand it right that there could be has claimed but because of newspaper style—it is perfect to use shorter past simple? Is it the same like: Three people killed in a car accident? Present perfect would be possible as well but it would be too long for this purpose.

2. Federer forgets he's won the match.
   source

This surprised me a lot. I thought it wasn't possible to use the present perfect in headlines.

• Why do you think the writer decided to use that tense? Was it for emphasis?

For me it is an unusual combination to use the present simple (forgets) and then the present perfect in newspaper headlines. The first is used to keep headlines short; however, in this case it doesn't make sense as it is followed by the longer present perfect construction.

The last thing is that I am not sure whether it is possible to switch tenses whenever I want. I´ll give you an example:

Headline:

Federer beats Djokovic in the 2nd round

The article

Federer has been beaten by Djokovic for the third consecutive time and will not defend his Wimbledon crown. Djokovic beats him easily and didn't allow him any break.

The thing I am not sure about is whether journalists can switch from one tense to another, see the following example: "Djokovic beats.." or whether it is acceptable to do so only in the headlines?