I only post framesets, and I take off the forks now to reduce the box size.
When I've previously taken boxed up frames which were a bit over the 150cm, they didn't usually check, I've only been called up on that once (a Trek mtb frameset with forks still in place, plus most of the bits, but not the wheels). It was also heavier than just framesets I've sent (11kg rather than about 5-6kg). They got the tape measure out that time, and the price went up from 30-something euros to 60-something euros.
I haven't tried shipping a full bike. You might have to break it down and send in mutiple packages. And maybe customise the frameset box into a diamond shape to keep the overall length/size down to less than 150cm.
I didn't know they'd introduced new Covid size restrictions. The box I'm trying to post looks quite compact, and it's quite a snug fit, but it's a bit over 150cm in total (a large size mtb frame). I'll see what they say when I take it back to the post office this weekend.