Learn English – What’s the meaning of “bulk rate”

In times past, the rule of law was caveat emptor, which is Latin for "let the buyer beware", placing the burden on the buyer to inspect goods before purchase, protecting those who would hide or falsify information about a product.

Relatively recently, this has changed to the need for full disclosure: the legal requirement to tell the "whole truth" about any matter which the other party should know in deciding to buy or contract.

There is the letter of the law and there is the spirit of the law. The letter of the law are the laws themselves; the spirit of the law is the principle behind the law (e.g. do not make false claims about your product).

There is no law that forces a writer to disclose every detail of how a particular situation came to be; there is likewise no full disclosure law governing something not bought (an article in an online magazine, for example.) So, writers will often cite the spirit of full disclosure to mean "full disclosure." It can be interpreted easily as

• In all honesty...
• Truth be told...

In this example, it is somewhat humorously used to disclose that the texter was someone she knew.

In all honesty, the texter in question turned out to be my editor at Salon...

Those 4 words above-mentioned are sometimes used interchangeably, but there are some clear distinctions.

Pace originally meant:

late 13c., "a step in walking; rate of motion," from Old French pas "a step, pace, trace," and directly from Latin passus, passum "a step, pace, stride," noun use of past participle of pandere "to stretch (the leg), spread out,"

[Online Etymology Dictionary]

Therefore, you use "pace" in place of speed to describe something slow and steady.

For example, you use a "pace-maker" in stead of "speed-maker" for your heart device or someone who sets the pace in a race such as marathon as it means:

A person or animal who sets the pace at the beginning of a race, sometimes in order to help a runner break a record

A device for stimulating the heart muscle and regulating its contractions.

[Oxford Online Dictionary]

However, if you describe a car or an airplane, you don't use "pace" for its "speed".

Tempo originally meant:

"relative speed of a piece of music," 1724, from Italian tempo, literally "time" (plural tempi), from Latin tempus "time, season, portion of time" (see temporal). Extended (non-musical) senses by 1898.

[Online Etymology Dictionary]

You also use "tempo" in place of speed to describe something slow and steady as it means:

The speed at which a passage of music is or should be played. The rate or speed of motion or activity; pace:

[Oxford Online Dictionary]

Rate originally meant:

"estimated value or worth," early 15c., from Old French rate "price, value" and directly from Medieval Latin rata (pars) "fixed (amount)," from Latin rata "fixed, settled," fem. past participle of reri "to reckon, think" (see reason (n.)). Meaning "degree of speed" (properly ratio between distance and time) is attested from 1650s. Currency exchange sense first recorded 1727. First-rate, second-rate, etc. are 1640s, from British Navy division of ships into six classes based on size and strength. Phrase at any rate originally (1610s) meant "at any cost;" weakened sense of "at least" is attested by 1760.

[Online Etymology Dictionary]

Rate is often used for "frequency" or "quantity".

‘the island has the lowest crime rate in the world’
‘buying up sites at a rate of one a month’

It can also mean:

"The amount of a charge or payment expressed as a percentage of another amount, or as a basis of calculation: ‘you’ll find our current interest rate very competitive’

(rates) (In the UK) a tax on commercial land and buildings paid to a local authority; (in Northern Ireland and formerly in the UK) a tax levied on private property.

[Oxford Online Dictionary]

You use "economic growth rate" not "economic growth speed" when it is expressed in a percentage.

Conclusion: The etymological roots of those four words can shed more light on their different usages.