Manual-protect at the peak of fighting

[PJ]

During some major Jin Ying fight scenes, it has been illustrated that fighters manually protect themselves by coating a layer of internal energy around their body, such that 3rd party outsiders cannot interfere with the fight. Examples include:

HSDS chapter 31:
左手一挥，又有三名好手上前夹攻。张无忌和玄冥二老此时各运神功，数丈方圆之内劲风如刀，那三名好手怎能插得下手去？

HSDS chapter 38:

周颠将狗腿往前一送，刚碰到渡厄口唇，突然间手臂一震，半身酸麻，啪的一声，狗腿掉在地上。原来渡厄此时内劲布满全身，已至“蝇虫不能落”的境界，四肢百骸一遇外力相加，立时反弹出来。

BXJ chapter 20:
孙仲君怒道：“别管我。我跟贼道拚了。”梅剑和道：“贼道已知小师叔的厉害，正用最上乘剑法护住了全身，你上去是白送性命。”孙仲君用力甩脱他手，叫道：“我不管，我去帮师叔。”她以前恼恨袁承志，从来不提“ 师叔”两字，这时见他与恶道为敌，竟然于顷刻间宿怨尽消。梅剑和道：“那你发一件暗器试试！”孙仲君取出金 镖，运劲往玉真子背后掷去。玉真子全神凝视袁承志的剑尖，金镖飞来，犹如未觉。孙仲君正喜得手，突听当的一 声，梅剑和失声大叫：“不好！”抱住她身子往下便倒。孙仲君刚扑下地，只见刚才发出的金镖镖尖已射向自己胸 前，全没看清那恶道如何会把镖激打回来，其时已不及闪避抵挡，只有睁目待死

In the above cases, if a 3rd party actually interfered, they would be killed by the manual-protect on the spot.

However, there is also the opposite case where the fighter involved is completely helpless to 3rd party interference:

DGSD chapter 40
虚竹自幼在本寺长大，下山半年，却不知从何处学了这一身惊人技艺回来，又见他抓住敌人，并不能制敌，但鸠摩 智每一掌中都含着摧筋断骨、震破内家真气的大威力，只要给击中了一下，非气绝身亡不可。此刻少林众僧中，不论哪一个出手相助，只须轻轻一指，都能取了鸠摩智的性命，但这番相斗，并非志在杀了对方，而是为了维护少林一派的声誉，若有人上前杀了鸠摩智，只有大损少林派令誉 。

Can anyone think of an explanation?

[kyss of the sword]

the first sitation may be one where there were focusing thier enegry to protect themselves and it mixed together to form a defensive force. while in the second, all their power was focused at a specific point and this left a huge gap for a third party to attack.