You`d better check the meaning of fluency again
It has different meanings in different sub-fields of language study.
en.wikipedia.org/wiki/Fluency
You're used to judging fluency in the context of a language classroom and/or oral exams where rapid speech with no fillers is valued. But that type of speech sounds awkward and off-putting outside of those contexts.
Sikorski's use of filler words is more or less naturally acquired from his long experience in English speaking intellectual environments. Words are measured and native and second language user alike will pause and (judiciously) use fillers while choosing words carefully.
or to quote from wiki again:
"Spoken language is typically characterized by seemingly non-fluent qualities (e.g., fragmentation, pauses, false starts, hesitation, repetition) because of 'task stress.' How orally fluent one is can therefore be understood in terms of perception, and whether these qualities of speech can be perceived as expected and natural (i.e., fluent) or unusual and problematic (i.e., non-fluent)"
Sikorski's seemingly non-fluent qualities are, in the opinions here of three different native speakers of three different varieties of English, very much in line with native norms.
Again, Trzaskowski's English is perfectly fine and he represents the country in English far better than say.... Duda but he doesn't sound like he's spent a lot of time in native environemnts (no reason he should). I might advise him to slow down a bit because at times he verges on the glib.