They have been crossings, camping and stopping Indian patrols at least since 2014. Chinese policy on LAC has drastically changed since Xi took over China. Chinese are looking and taking advantage of every opportunity to grab more Indian land.
It is foolish to think that they will stop their forward march at that fictitious LAC. Chinese foreign minister clearly stated that they do not recognize LAC back in 2008 itself.
China agreed to PVN's LAC proposal back in the 1990s as they were still not strong. Since 2008 financial crisis Chinese have gone strength to strength and have simply discarded the agreements that they signed with India on LAC.
China, India in border skirmish ahead of Xi visit
https://www.hindustantimes.com/indi...of-xi-visit/story-es46bqLyFXY5qgosyMnQAK.html
For now China has shown no desire to de-recognize the LAC. Their aggressive stance could very be their lame attempt to bully India only to find it spectacularly back fired.
Both India and china patrol their own claim line. India go up to finger 7 and sometimes upto 8 and china patrol upto finger 3.
Same with every other patrol points along the LAC. From Ladak to Arunachal Pradesh.
They stop our patrol and we stop their patrol. Only our Media uses this opportunity to get some more Viewership and make some more money by increasing their TRP.
What changed this time was the death of our men and India wants to ensure that it never happens again.
The last thing Xi wants to do is stir shit along the Indian border.
The reason for that is simple.
When China and India go up face to face, china being the stronger nation appears weak and India being the weaker nation , we appear strong.
Since the entire chinese philosophy is based on "perception management" a.k.a "saving face", they have realized that during the Doklam Standoff its India that come out ahead in the global stage and they were always keen to avoid any such situation again.
It also encourages the world to think of India and China in the same vein and China desperately wants to avoid that. The same way we hate being linked to pakistan.
That being said, maybe there is some other play so we are careful and preparing for the worst.