CM870 loosing coolant/possible inflame

[Koren]

Hi, everyone.
I have 07 Volvo with CM870 in it, 1.4mil miles. No known inframe history. Mandate deleted. I noticed that it started smoking on the initial start up.
https://youtu.be/-LnKdPSLcsk

It smokes like that for about 1-2 minutes and then smoke goes away.
Also I'm loosing coolant. Can't exactly say how much of it. Looks like loosing more under pressure and less when I drive empty.
On top of that I'm having a hard time starting the truck. It feels like starter got stuck trying to turn crankshaft.
https://youtu.be/-LnKdPSLcsk

This video i shot after about 2 hours trying to start it. When I continously trying, the smoke and burning smell comes out of the starter. So I didn't push it much, just did couple of tries every 10-15 min.
The starter is 7 months old, batteries are less than 2 weeks old.
Having the starter on warranty but mechanic told me it is not the starter issue. He said that the coolant is leaking inside the engine and doesn't let piston move to compress the air. However when you move it to the point when valves starting to open up - coolant escapes and let the starter do its job.
Does that make any sence?? Or he is trying to avoid replacing my starter under warranty?
Even if cut off the engine and trying to start it back up right away - it is not cranking with a full speed like it suppose to. It does it very slowly and I can barely start it. Mechanic says I have to open up the engine, fix the internal coolant leak issue in order for it to move freely.