From the full list, I think the main problem is that apparently it is of 'underreported' attacks, or so I interpret their intention.
Orlando? Boston, as you mentioned? Charlie Hebdo? Bataclan? Brussels? Berlin? Russian plane crash? I can't actually speak for US coverage (who may well have ignored Tunis/Bardo and Souse), especially at the latter end of that short extract of the list, but at least a week of solid follow-up headlines happened with these and others, and often many weeks, months, anniversary coverages...
The BBC's 'self-confessed failures' are:
a Danish man wounded in Riyadh, November 2014 (covered by Reuters)
two US citizens under fire in 'Riyadh', January 2015 (probably a misplacement of an actually reported incident elsewhere)
one US citizen wounded by knife in Karachi, April 2015 (a relatively small incident compared to more serious reports from there)
an arrest of a man in Paris, April 2015 (not exactly a stand-out, SFAICT)
Peacekeeping force camp attacked at El Gora, Egypt, June 2015 (peacekeepers are always targets)
Peacekeeping force camp attacked at El Gora, Egypt, September 2015 (there you go, and the general situation was reported)
Palestinian asylum-seeker attacks policeman in Copenhagen, September 2015 (apart from the trigger words, wasn't even the worst incident there, that month)
It took a while to report Merced, California, November 2015 (student knifes four people, IS 'links' brought up only months after)
Teenage girl 'IS sympathiser' wounds policeman in Hanover, Germany, February 2016 (details given only upon comviction)
Possible failed lorry-bomber supposedly attacks US personnel but fails to injure anyone but himself in Kuwait City, Kuwait, October 2016 (unclear even if this was an event, a non-event, an accident, etc)
A minor fire in Malmo, Sweden, October 2016 'claimed' by IS (but very little reason to give credance to that)
A 16yo killed by knife in Hamburg, October 2016 (local news only, doubtful connection of this tragic but otherwise not untypical 'normal' crminal act)
Suspected bomb did not explode outside US Embassy, Manila, Philippines, November 2016 (local media promoted IS link, but who knows)
Person(s) unknown fired shots at US Embassy, N'Djamena, Chad, November 2016 (not really so notable, without further knowledge to back it up)
I think I 'forgive' those 'failures', personally. The number of deaths (or even injuries or 'slight concern for safety') in all those missed items is dwarfed by dangerous driving road traffic accident deaths, unconnected homicides, seasonal flu deaths or whatever, each of which deserves reporting at least as much attention as an issue to make those low rates potentially even lower by education and awareness of the issues.
But that's my opinion..